Southern Pacific Signal History

The first part of this report looks at the history of the western portion of the Southern Pacific from El Paso and New Mexico westward to the Pacific Coast and northward to Portland, OR and the original Central Pacific line to Ogden, UT. This will include signals installed by the El Paso & Southwestern before being merged with the SP in late 1924. Much of this information has been gleaned from various Railway Signaling and Communications books.

The SP installed one arm lower quadrant semaphore signals between Bakersfield and Mojave in 1901.

In 1909 the SP was adding signals between Gila and Esrella, AZ 19 miles and adding 53 miles of US&S Style B signals between Cornutt and Hugo, OR through Cow Creek Canyon.

In 1912 SP began installing more semaphore signals between Ashland, OR and Eugene on the Siskiyou Line. The line was built around 1887. Central Oregon and Pacific removed the signals between 1998 and 2007.

semaphore signals on the Siskiyou Line

In 1914 the El Paso and Southwestern (EP&SW) had completed installation of 140 miles of block signals bringing the total to 159 miles. It planned to add 29 more miles of signals between Whetstone, AZ and Lewis Springs.

In 1914 the SP completed 23 miles of new section of double track and added 38 miles of semaphore signals between Sparks, NV and Truckee, CA. This brought the total of miles protected by automatic block signals to 2,397 miles of single track and 389 miles of double track. The SP installed a 16 lever US&S mechanical interlocking plant at Flannigan, NV.

It planned to add an 80 lever GRS interlocking plant at Davis, CA, a 24 lever GRS interlocking plant at Bloomington, and a 107 lever GRS interlocking plant at Fourth St in San Francisco in 1915.

During 1916, the EP&SW added signals for 20 miles west of El Paso

At the beginning of 1917, the SP (Pacific Lines) had automatic block signals on 2,397 miles of single track and 408 miles of double track while the EP&SW had automatic block signals on 213 miles of single track of the 816 miles it operated.

EP&SW order 122 US&S upper quadrant signals in 1917. The next year it installed block signals on 14 miles of single track between El Paso and Mastadon, NM, 39 miles of single track between Moores Spur, AZ and Pratt, NM, 25 miles of single track between Lewis Springs, AZ and Osborn.

In 1919 the EP&SW completed installation of block signals on 19 miles of single track between Forrest, AZ and Lee. By the end of 1919, the EP&SW had 310 miles of single track with automatic block signals.

In 1919 the SP added a second track and completed installation of block signals to 12 miles of double track between Kern Jct and Sivert. By the end of 1919, the SP Pacific Lines had 2,245 miles of single track and 508 miles of double track with automatic block signals out of its 7,588 miles.

The SP began adding double track south from Bakersifield in 1919. Double track from Cameron to Mojave was completed in August 1923. In 1922 it installed 24 US&S style B lower quadrant semaphore signals to a 17 mile segment of double track and finished the signal installation in 1923.

In 1921 the EP&SW had automatic block signals between Santa Rosa and Guadelupe (northeast of Pastura) and between Winkle (southwest of Pastura) and Carrizozo. The rest of the line between Tucumcari and El Paso was dark territory.

In 1923 SP installed
77 US&S semaphore signals between Grants Pass, OR and Woodburn 51 miles,
10 US&S semaphore signals between Wells, NV and Moor 9 miles of double track,
24 US&S semaphore signals between Snowden, CA and Hornbrook 14 miles,
14 US&S color light signals between Blue Canyon, CA and Emigrant Gap 5 miles of double track, and
20 US&S color light signals between Andover, CA and Truckee 6 miles of double track.

In 1923 SP installed a 12 lever mechanical interlocking at Merced, CA.

SP completed a second track between Tehachapi and Cameron in June 1924.

In 1925 SP installed US&S semaphore signals
Folk, OR and South Salem 12 miles 20 signals,
Wilbur, OR and Yoncalla 15 miles 24,
Elmhurst, Ca and Santa Clara 31 miles 31 signals,
Yuma,AZ and Ivolan 5 miles of double track 16 signals, and
installed 74 US&S color light signals between Santa Cruz and Seabright 30 miles of double track.

semaphore signals at Yoncalla

In 1926 In 1926 SP continued signal work begun in 1925, installing
183 color light signals Black Butte, CA to Klamath Falls, OR 84 miles,
375 US&S type B semaphore signals for Klamath Falls to Springfield Jct. 192 miles,
36 US&S type B semaphore signals from Dome, AZ to Wellton 18 miles of double track, and
60 color light signals Emigrant Gap to Andover 30 miles of double track.

In 1926 on the Sunset Route there were automatic block signals between Tucson and Lordsburg, except for 13 miles on Track 1 between Vail and South Yard Jucntion. There were three areas of automatic block signals between Lordsburg and Mongola (five mile east of Gage), Camp Cody for two miles to Deming, and Strauss to El Paso. There were two areas of automatic block signals on the EP&SW between Mescal and Pratt (12 miles east of Rodeo) and Mastodon (eight mile west of Anapra) to El Paso.

semaphore signals east of Vail, AZ

In 1926 the SP added a US&S interlocking at Mescal, AZ. The unit was in the old EP&SW station and had 9 levers to control switches and 8 levers to control signals, plus one lever to control the lock on a hand operated switch. West of Mescal the SP used the EP&SW line for westward trains and the original SP line for eastward trains. The EP&SW line bridged over the SP line at the east end of Mescal. Connector tracks were added so trains could use either line east of Mescal. A similar desk type US&S 9 lever interlocking panel was installed at Wellton, AZ.

The Santa Clara Interlocking Tower was built in 1926 and became operational in 1927. It had a GRS Model 2, with 34 working levers type electro-mechanical interlocking machine. The tower was closed in July 1993.

In 1927 SP installed added 217 US&S type B semaphore signals on the original Sunset Route from Wellton, AZ to Picacho on 124 of the 166 miles.

\sp In 1928 the SP changed the signal system over the Tehahapi grade by adding 11 power switches and 13 spring switches. The power switches could move from normal to reverse or back in 17 seconds and were controlled by the local station agents. Power switches were at east and west Caliente, east Allard, east and west Bealville, east and west Woodford, east and west Marcel, and a crossover at Tehachapi. Spring switches were at end of double track west of Tehachapi, west Cable, east and west Marcel, west Walong, west Cliff, east and west Bealville, west Allard, east and west Caliente, east end of double track and siding switch at Bena. The line also had M and S indicators on sgnals at hand operated switches. M meant hold on main track and S meant head into siding. For example the station at Bealville controlled the east Allard, east, and west Bealville power switches and the M and S take siding lights at the west end of Allard.

In 1928 on the Sunset Route, there were automatic block signals from Yuma thru Gila Bend to Estrella, a short stretch around Maricopa, and from Eloy (4 miles west of Picacho) to Ocatilla (three miles east of Picacho), a short stretch around Red Rock, and from Stockham into Tucson. During 1928 SP added 97 US&S style B semaphore signals from Picacho to Stockham. It also added US&S style B semaphore signals Picacho, AZ to Stockham (Tucson) 40 miles 97 signals and Vail to Polvo (Tucson) 13 miles 8 signals on Track 1. Elsewhere on the system, it added an automatic interlocker at Flanagan, NV at the WP crossing and added 165 US&S searchlight signals Davis, CA through Woodland to Tehama 111 miles. That line had about 20 trains a day in 1928. It ordered color light signals to add 800 miles of new signals to its remaining main lines and some branches on the Pacific Lines. The project cost is $2.5M and includes the relocation of 500 miles of semaphore signals.

In 1929 on the Golden State Route SP installed 33 US&S semaphore signals between Temporal, NM and Carrizozo 35 miles. The following year it planned to add 142 signals between Temporal, NM and El Paso 99 miles. It would then focus on the El Paso Southwestern and add 202 signals between Mastadon and Pratt, NM 132 miles.

In 1929 On the Sunset Route SP installed 152 US&S semaphore signals on 94 miles of single track between Ming (5 miles east of Wellton on the Phoenix line) and Picacho, AZ 94 signals from Estrella to Picacho, AZ 60 miles, and 142 semaphore signals from Mongola, NM to Strauss 81 miles.

In 1929 SP installed 51 US&S semaphore signals on 43 miles of single track somewhere between Ashland, OR and Roseburg, 13 signals from Gazelle, CA to Montegue 11 miles, 85 signals on 69 miles of single track between Roseville, CA and Tehama.

By 1930 the SP had installed automatic block signals between Santa Rosa, NM and Paxton (about 12 miles northeast of Orogrande) and between Alvarado (about 10 miles northeast of Newman) and El Paso. In 1930 the SP ordered 72 one arm and 19 two arm semaphore signals from US&S to be installed between Santa Rosa, NM and Tucumcari 55 miles.

In 1930 for the SP Pacific Lines, the first CTC installation was completed between El Pinal (near Stockton) and Polk (near Sacramento) 39.7 miles in April 1930. The CTC machine had 35 switch levers and 29 signal levers and was installed in Stockton. At the time, the traffic on the line varied from 9 passenger and 9 freight trains a day in January to 9 passenger and 37 freight trains a day in September. The harvest season was the reason for the wide numbers. Typical empty reefer trains were usually 100 to 125 cars while loaded trains were between 70 and 74 cars. The was so much growth in perishable traffic in the valley that the SP was considering double tracking the route at a cost of $2.5M.

In 1930 SP added a GRS model 2 56 lever interlocking at Norden, CA to control 8 switches, 5 crossovers, 4 derails and 62 signals. Helpers are cut out of all heavy freight trains and the engines turned on the turntable between the two main tracks. At the time there were 6 passenger and 16 freight trains a day. During 1929 there were up to 36 freight trains a day. It also added an interlocking at Carlin, NV.

The $12M double track Suisun Bay bridge was completed in October 1930 to replace the ferry system of getting trains between Sacramento and Oakland. The line handled 24 passenger trains and about 12 freight trains a day. The bridge is 70 feet above the water so only needs to be raise two or three times a day. The US&S electro pneumatic interlocking machine is in the control room on top of the 336 foot verticle lift span. A US&S electric interlocker desk console was added at the Martinez depot to control the switch to the Mococo line to Tracy.

Southern Pacific had block signals on most of its mainlines by 1931. It added 17 color light signals from Gilroy, CA to Seargent on 5 miles of double track and added GRS model 2 electric interlockers in California: 21 levers at Newark and 40 levers at Dayton Avenue in Los Angeles to control 18 switches.

By 1939 the SP had completed the installation of signals on the Golden State Route between El Paso and Tucumcari.

semaphore signals on the Golden State Route

Prior to World War II, SP had one installation of CTC in California, covering about 40 miles. Total mileage under CTC operation at end of the war was 375.2 miles, costing about eight million dollars, including incidental track changes. In 1942 SP began installing CTC Redding to Delta, 30.1 miles, completed in March, reached Dunsmuir in June 1942, and Black Butte in November. It also installed CTC from Santa Margarita to San Luis Obispo, 16.6 miles completed in August. The Cuesta CTC machine was located at the SLO depot until 1964, when it moved to Third and Townsend. Also in 1942, US&S interlockings were installed in the stations at Vincent and Saugus to speed up operations. Each panel controlled 2 switches and 8 signals. Spring switches lined trains either into the westward or eastward sidings at each installation.

In 1943 it installed CTC from Bena to Tehachapi, 32.3 miles completed in June. The CTC machine was in the Bakersfield passenger depot. The SP then shut down the train order offices at Bena, Caliente, Bealville, Woodford, and Marcel.

In 1944 SP continued adding CTC from Beaumont down the east side to Indio completing the Colton to Indio, 70.8 miles project in April. The US&S CTC machine was in Beaumont until moved to LA in 1958. It had 111 levers controlling 36 switches. It installed CTC in Nevada, between Vista (near Sparks) and Massie, 43.5 miles completed in August. The US&S machine controlled 29 power switches.

In 1945 CTC was installed from Bridge Siding across the Great Salt Lake cut-off to Lemay 52.8 miles completed in May. The CTC machine was at Ogden 30 miles away. The SP replaced semaphore with color light signals from Truckee to Lawton, NV 29 miles.

In 1946 Under construction for completion in 1946, was 21.1 miles of CTC from Lucin to Lemay, UT. SP also removed 42 semaphore signals, converted 50 to color light and added 20 new color light signals between Massie, NV and Perth 48 miles.

The SP removed 19 semaphore signals, converted 43 to color light and added 14 new with color light signals between Gaviota and Santa Barbara 30 miles in 1947.

In 1948 CTC was installed between end of double track in Alhambra to Colton 50 miles. The US&S CTC machine had 52 levers controlling 25 switches.

In 1949 Taylor Yard was constructed in 1925 and could process 1,500 cars a day in the late 1940s. In 1949, the SP decided to replace the rider operated hump at Taylor Yard with retarders. The old hump yard had a capacity of 958 cars, the new hump 1,237 cars. At the time the SP was handling about 600 cars a day to and from local industries. It also interchanged around 500 cars a day with other railroads in Los Angeles.

In 1950 SP planned to replace old semaphore signals with searchlight signals Braymill, OR to Chemult, Turlock, CA to Chowchilla and at Goshen Jct. in the Valley, San Luis Obispo to Carmalia, and Montalvo to Chatsworth on the Coast.

Around 1950 Davis Monthan Air Force Base in Arizona wanted to expand. To accommodate the expansion, the SP added a second track following the EP&SW from the east end of the yard in Tucson to near Vail in 1951. The railroad then ripped out the original track put down in 1880 between these points. New US&S searchlight signals were installed in 1952 from Polvo to Vail 15 miles.

In 1952 Construction of Lookout Point Reservoir in Oregon in 1952 forced SP to relocate 25 miles of the Cascade Line south of the original alignment. New US&S searchlight signals were installed in 1952 from Jasper to Lookout.

In 1952 SP was installing radio equipment in snow fighting equipment and wayside stations on Donner, Siskiyou, and Cascade passes.

Between 1953 and 1958 the SP replaced semaphore signals with searchlight signals between Mojave and Burbank Jct.

In 1953 SP installed CTC Klamath Falls to Cresent Lake 100 miles. CTC machine at Dunsmuir. At the time the line had 6 passenger and 14 to 18 freight trains a day. SP installed 53 loudspeakers in the yard at Sparks, 74 at Phoenix, and 67 at El Paso. SP modified the interlocking at El Monte, CA to contol five signals and one signal and the interlocking at Hanford, CA to control five signals and five signals.

SP ordered US&S CTC for Cresent Lake to Eugene, OR 95 miles in 1953. Intallation began in October 1953 and was completed in 1954. The CTC machine controlled 45 switches and 200 signals. In 1954 SP replaced semaphore signals with searchlight signals, added spring switches with facing point locks, and lengthened sidings between Tucson and Picacho on four miles of double track and 43 miles of single track. At the time the line had 11 passenger, four scheduled freight and around eight extra freight trains a day. The SP replaced the mechanical interlocking with a relay interlocking at Niles Tower.

In 1955 SP and WP planned to modify the interlocking at North Stockton, CA. The mechanical interlocking would be removed and electric interlocker installed controlled by the SP dispatcher. The SP added nine miles of double track to west side of Beaumont Hill.

In 1956 SP began installing CTC Indio to Yuma 114 miles in 1955. It added a second track from Indio to Thermal, added a new siding at Ferrum, removed short sidings at Durmid, Pope, and Mundo, then lengthened other sidings to at least 9,000 feet, installed 45 power switches and 232 signals. The work was completed in June 1956. Also during this time it lengthend and connected 14 sidings into six sidings on Beaumont Hill. More specifically connecting Ordway and El Casco, connecting Hinda, Nicklin, and Beaumont, connecting Owl and Cabazon north siding, connecting Cabazon south siding, Mons and Fingal, and connecting Hugo and Garnet sidings. At the time, the line had eight passenger and better than 20 feight trains a day plus returning helpers. During the sugar beet harvest the SP moved 11,000 cars out of the Imperial Valley. Also in 1956, SP installed a US&S interlocking in the depot at Mojave to control four signals and nine power switches at East Mojave. It installed one of the first microwave systems from Dunsmuir, CA to Black Butte and installed cab signals in hump engines at Eugene, OR.

In 1957 SP rebuilt the interlocking at Weso, NV with two US&S switches and 4 signals and the interlocking at Alazon, NV with two US&S switches and 3 signals.

The next couple years were busy times for CTC installations especially on the Sunset Route.

In 1958 SP planned to install CTC Mescal, AZ to Lordsburg, NM 124 miles and incorporate the interlocking at Mescal. Part of the project will remover four sidings and lengthen 14 other sidings to at least 9,000 feet and add two new sidings. Work was completed in 1959 after installing 39 power switches and 228 signals.

In 1959 Major work was done on the line during the installation of CTC east of Tucson in 1959. All sidings were lengthened to at least 171 car lengths.The double track between Tucson and Mescal continued as it had before with westbound trains using the newer and better built EP&SW track and eastbound trains using the old SP trackage.

In 1959 ordered US&S CTC for Lordsburg to Anapra, NM 145 miles. Work was completed in 1959 after installing 34 power switches and 230 signals. The CTC machine for Tucson was the new push button US&S TCC (traffic control center) style and will control 270 miles Tucson to Anapra. The CTC machine was the new push button US&S TCC (traffic control center) style and would control the territory from Mescal to Anapra (west of El Paso). Tucson Division CTC machines were in a small building east of the passenger station at Tucson. The Gadsden-Pacific Division Toy Train Operating Museum, 3975 N. Miller Ave. in Tucson has the Yuma to Tucson CTC board.

In 1959 SP ordered CTC for Tucson to Gila Bend, AZ 128 miles. In late 1959 planned CTC Yuma, AZ to Gila Bend 121 miles. The territory will be added to the new push button US&S TCC (traffic control center) style CTC machine in Tucson.

In 1960 SP completed CTC installation Yuma, AZ to Gila Bend on May 17, 1960. This give the RR 810 miles of either double track or 59 sidings under CTC control from Los Angeles to El Paso, TX.

Meanwhile in Nevada in 1958 SP installed US&S CTC Moor to Valley Pass, NV 22 miles 4 switches 36 signals. All controls were moved to Ogden. SP planned to install CTC Massie to Perth, NV 47 miles. After installing 11 power switches and 46 signals the project was completed in 1959. At the eastern end of the division SP also installed CTC from Tresend, UT to Bridge 12 miles with three switches and 21 signals in 1959.

Meanwhile across the rest of the system in 1958 SP installed a US&S interlocking at Texum, OR controlling one switch and three signals for the Modoc Line. Around 1959 CTC was extended from Bena to Sandcut with the installation of a double crossover and the middle siding at Bena removed. Between September 1959 and April 1960 south of Mojave, the sidings at Ansel, Oban, and Denis were lengthened and the sidings at Rosamond and Gloster were removed in preperation for the addition of CTC. Several signals were removed and some moved to form longer blocks between Ansel and Oban. Interesting that this was one of the last stretches between Texas and Oregon to get CTC. In 1960 SP added control of five signals to the interlocking at Mojave. I think this was in conjunction with the removal of the north end switch tender at Mojave. Trains then had to line themselves into or out of the yard. SP planned to install CTC on the south track between Cameron and Mojave 10 miles. This work was completed in 1961.

The 1960s brought more CTC to the lines in Oregon, the Central Valley of California and Nevada. In 1962 SP installed CTC between Bakersfield and Fresno.
CTC installed between Biola Jct. and Lathrop during 1962-63.
CTC installed between Whitney and Gerber during 1963-64.
In 1964 SP opened a new dispatchers office in Roseville and moved dispatchers from Ogden to Roseville.
CTC installed between Black Butte and Klamath Falls in 1965.
CTC installed between Truckee and Switch 9 during 1966-67.
CTC installed between Weso and Rose Creek in 1970.

Around the rest of the system, the SP began operating over the WP between Flanigan (Modoc Line) to Winnemuca in 1963 and installed a microwave system between Bakersfield, Lancaster, and LA in 1964.

In 1974 SP began replacing some of its older signals with tri-light signals.

new tri-light signals

SP cut in CTC West Colton to Palmdale in December 1979.

SP installed CTC between Mojave to Palmdale in 1980.

In 1989 Roseville dispatch center opened in the Fall of 1989. It combined the dispatcher offices from Eugene, Tuscon, and Los Angeles. The system used Digital Traffic Control (DigiCon) computer systems.

In 1996 it removed the second track between Rose Creek and Perth, NV and installed CTC.

In 1997 Metrolink installed CTC between Lancaster and Burbank Jct.

CTC was installed on the El Paso to Tucumcari line in 1999.

Eastern Lines

The second part of this report looks at the history of the eastern portion of the Southern Pacific and predecessor railroads in Texas and Louisiana. Many of the short lines in Texas and Louisiana were merged into the Texas and New Orleans by 1936. The T&NO was merged into the SP in 1961. The SP gained control of the St. Louis & Southwestern in 1932, but ran it as a separate company until 1992.

Signals on Sunset route in Louisiana and Texas as of July 1, 1909
Avondale to Morgan Ciity 68 miles and Lafayette to Lake Charles 72 miles on the Morgan's Louisiana and Texas Railroad
Lake Charles to Sabine River 31 miles on the Louisiana Western Railroad
Echo to Beaumont 26 miles, Beaumont to Englewood 77 miles on the Texas and New Orleans
Houston to Glidden 86 miles, Glidden to Seguin 87 miles on the Galveston, Harrisburg, and San Antonio Railway
there are a few other short stretches not shown in the total of 495 miles.

In 1909 the GH&SA planned to start adding signals between Seguin and Gulf Jct 30 miles and Del Rio to Langtry. Del Rio to Langtry 65 miles completed 1910.

In late 1915 the GH&SA planned to install a 16 lever mechanical interlocking at the crossing of the I&GN at San Antonio.

In 1917, the Houston and Texas Central installed 23 single arm and 1 double arm US&S style B signals around Hempstead, TX.

In 1919 GH&SA added four levers to the mechanical interlocker at Flatonia, TX.

In 1923 GH&SA ordered 45 US&S lower quadrant semaphore signals for station protection at the following stations located between San Antonio and El Paso: Uvalde, Noonan, Sabinal, Alpine, Toronto, Paisano, and Marfa. Constructin was in progress at the beginning of 1924. The 13 miles from Alpine to Toronto received 18 signals. The other five stations received 6 signals each stretched across about five miles plus Spofford and Macdona also received 6 signals each. Signals were coming to the Sunset Route in little chunks. The railroad added 2 electric levers to the interlocking at Hearne, TX; installed a 10 lever mechanical interlocking at Sugarland, TX; and added 2 levers to the mechanical interlocking at Harrisburg, TX.

In 1924 GH&SA ordered 30 one arm and 5 two arm US&S lower quadrant semaphore signals for installation between Cline and Hacienda and between Noonan and LaCoste, TX. T&L added one lever to the mechanical interlocking at Flatonia, TX to control 2 remote power switches, added three levers to the mechanical interlocking at Beaumont, TX; and added two levers to the mechanical interlocking at Kaufman, TX.

In early 1924, the railroad ordered 132 one arm and 44 two arm US&S lower quadrant semaphore signals plus 487 relays for installation from Hot Wells to Ysleta 102 miles. By the end of 1924 it had added 189 signals from Ysleta to Grayton 88 miles. It also added 20 signals between Hammond and Bremond, TX 10 miles. It also ordered a 40 lever GRS model 2 interlocking machine for Eagle Lake, TX.

In 1925, the railroad was adding 45 US&S lower quadrant semaphore signals from Grayton to Hot Wells. Completed in 1925 along with Hot Wells to Seirra Blanca 25 miles 61 signals. It also installed 68 one arm and 21 two arm US&S semaphore signals from Osman to Sanderson, TX; 76 one arm signals and 27 two arm signals for Withers, TX to Cline 65 miles; 21 one arm signals from Eureka, TX to Cypress; Courtney, TX to Navasota 7 miles 23 signals; 7 two arm signals for Avondale, LA to Harvey; and 17 one arm signals and one two arm signal for Avondale, LA to Algiers. It ordered a mechanical interlocker for the crossing of the Texarkana & Fort Smith (KCS) at Port Arthur, TX. This would become Tower 120.

In 1926, the railroad ordered 238 one arm and 89 two arm US&S semaphore signals for Sanderson, TX to Marfa 103 miles, Cline to Del Rio, TX 55 miles, and Hearne, TX to Mexia 53 miles. By the end of 1926, it had added 113 signals Cline to Del Rio, TX; 22 signals Osman to Langtry; 160 signals Longfellow to Marfa; 115 signals Hearne to Mexia; 19 signals Miller Yard to T&P Jct. 8 miles. A separate pole line was used for signal operations. The poles were set 40 to the mile. At the time a pole cost $6.25 and it cost $1.50 to set a pole. A special grounding wire is set above the crossbar carrying all of the block signal wires for lightening protection. The wire runs to ground every fourth pole. GH&SA ordered a GRS model 2 interlocking machine with 7 levers for Tower 121 in San Antonio, TX. H&TC added a reconditioned GRS 43 lever interlocking machine to Tower 118 Belt Jct and ordered a 33 lever GRS model 2 interlocking machine for Ennis, TX. Included in the order were 17 one arm, two three arm semaphore signals, and 8 power switches.

In 1927, the railroad ordered 271 one arm and 86 two arm US&S semaphore signals for Marfa to Hot Wells, TX 81 miles and on the H&TC Navasota to Hearne and Mexia to Dallas.

In 1928, the railroad added US&S style B semaphore signals Corsicana to Miller Yard in south Dallas 44 miles 111 signals and added a desk interlocking panel at Ennis to control the junction switch at Garrett. It ordered 47 one arm, 12 two arm US&S type B semaphore signals, and 100 relays for Flatonia, TX to Glidden 39 miles. Corsicana to Ennis signal installation was still in progress in 1928. When completed there was automatic block signals from New Orleans to El Paso 1,190 miles and Dallas to Houston 263 miles.

semaphore signals at Rice, TX

In 1929, the railroad installed US&S mechanical interlockers in Texas:
10 lever at Tatsie (Tower 140),
8 lever at Edcouch (Tower 146),
8 lever at Latana (Tower 147),
8 lever at Rosita (Tower 151), and
installed GRS electric interlockers at:
15 lever at Englewood Yard (Houston)
11 lever at Waco, and
6 lever at Eureka.

Also in 1929, the SSW installed three US&S automatic interlockers in Arkansas: Jonesboro (SLSF), Fair Oaks (MP), Camden (MP).

The railroad added US&S semaphore signals from Beeville, TX to Skidmore 11.3 miles in 1929. This became the first CTC on SP System, in service Jan. 18, 1930. The installation controlled 4 switches at two sidings (Darby and Yougeen) and used 25 semaphore signals. The CTC machine was at the station in Beeville. At the time the line had six passenger and six freight trains a day plus two locals. However during harvest time in the Rio Grande Valley in February and March the line could see up to 40 trains. Retired in 1981.

the first CTC on SP System

In 1930 it had several US&S electric interlockers being installed in early 1930 at Sanderson and Sierra Blanca, TX.

Later in 1930, it ordered its second CTC installation for Alpine Junction, TX to Paisano 12 miles. The installation controlled 4 switches at two sidings, 2 junction switches, and used 34 semaphore signals and 120 relays.

In 1936 the T&NO added a GRS electric interlocker at West Bridge Jct, LA with 24 levers.

In 1941 SSW and MP trains used MP tracks jointly from East St. Louis to Thebes and SSW track from Illmo to Dexter. Thebes to Illmo was jointly owned. SSW installed 76 US&S color light signals Illmo to Dexter in 1941 on 32 miles of single track and 14 miles of double track. The segment from Illmo to Dexter remained busy after the war with around 60 trains a day in 1957.

tno In 1942 T&NO installed CTC in San Antonio between Tower 26, and Niles 2 miles.

During 1943, T&NO installed CTC between Belt Junction Tower and T & P Junction Tower 4 miles and between Ennis and Garrett 1 miles on the Dallas Div. Garrett was reclassified as interlocking 1988 then as CTC in 1994. Also in 1943 SSW installed CTC between Northern Illmo, MO and Dexter Junction, 50 miles (includes 15 miles with two main tracks).

In 1944 T&NO CTC installed from Nacogdoches, TX to Bonita Junction 2 miles. This was reclassified as A-PB from 1958 to 1981, then reverted to ABS. And CTC installed from Tower 86 to Harrisburg Junction 3 miles on the Galveston Sub. SSW ordered US&S CTC for Fordyce, AR to Lewisville 84 miles. The machine would be at Pine Bluff. SP opens its new Pecos River bridge, a 320 foot-high steel cantilever structure December 21, 1944.

In 1945 SSW installed CTC Texarkana to Pine Bluff, AR. T&NO changed some signals and relocated others in the 10 miles between Flatonia, TX and Muldoon.

In 1946 T&NO installed CTC from Sherman, TX to Denison 8.5 miles on the Dallas Div. Sold to BN in 1993.

As of July 1, 1946 SSW had no signals in the following areas where passenger trains exceeded 60mph and freight trains exceeded 50mph:
Dexter to Pine Bluff 233 miles 15-25 trains/day
Lewisville to Texarkana 29 miles 17 trains/day
Lewisville to Shreveport 62 miles 10 trains/day
Texarkana to Corsicana 202 miles 16-21 trains/day and
Mt Pleasant to Dallas 133 miles 8-12 trains/day.

In 1947 SSW installed US&S CTC between Lewisville, AR and Gertrude 25 miles. The machine had eight levers controlling three switches.

Plans were made to modify Tower 6 and 47 in El Paso from mechanical to power operation in 1948. It would close Tower 6, install all relay interlocking in Tower 47 and add new Tower 196 at the west end of the passenger station. This project was finished in 1950.

In 1951 T&NO installed CTC Austin, TX to Pershing 2 miles. This was reclassified as A-PB in 1958 and retired in 1970. SSW installed an automatic interlocker in Waco, TX that controlled four signals.

In 1952 SSW installed US&S CTC between Brinkley, AR and Pine Bluff, AR 68 miles. T&NO installed CTC Harrisburg Junction, TX to Tower 17 34 miles on the San Antonio Div. Semaphore signals replaced with searchliight signals. The CTC machine was in San Antonio. At the time, the line had four Santa Fe passenger, four SP passenger, four freight trains, and several locals each day.

In 1953 T&NO installed CTC from Tower 87 to Tower 26 (4 miles) in Houston and installed CTC from Avondale, LA to Salix 6 miles on the Lafayette Div. The later installation was retired in 1959 or 1960.

In 1953 SSW ordered and installed CTC Dexter Junction, MO to Jonesboro, AR 84 miles. Initially the CTC machine was to be at Illmo but was installed in Pine Bluff. SSW also ordered US&S CTC for Pine Bluff, AR to Gertrude 27 miles.

In 1954 SSW installed US&S CTC Texarkana, AR to Mount Pleasant, TX 60 miles on its Texas Div. and installed CTC from Jonesboro, AR to Brinkley, AR 71 miles (CTC machine controlled 13 switches and 90 signals).

In 1955 SSW installed CTC from Mount Pleasant, TX to Tyler 68 miles on its Texas Div.

In 1956 SSW installed CTC from Tyler, TX to Corsicana 75 miles. This was the last segment of CTC to be added on the SSW. At the time, the line had 10 to 12 trains a day. The T&NO installed US&S CTC Hearne, TX Seger, TX 4 miles to control two switches and nine signals.

In 1958 it was time to improve interlocking facilities. T&NO and Texas City Terminal planned to replace the mechanical interlocking at Texas City Jct, TX with an automatic interlocker. T&NO planned to replace electric interlocking at Tower 38 (crossing the Santa Fe) in Galveston, TX with an automatic interlocker. T&NO planned to install additional interlocking controls in Tower 87 in Houston to control traffic between Dawes and Fauna 3 miles. T&NO, SSW and MKT planned to replace the mechanical interlocking at Waco, TX with an automatic interlocker.

In 1959 T&NO and the Missouri Pacific agreed to install CTC from the east end of Belen Yard in El Paso to Sierra Blanca 75 miles. Work began in 1959. After installing 19 power switches and 92 signals, the work was completed in 1960. Control machine was in Houston.

In 1963 the SP extended CTC from Seger, TX north to Bremond, TX 19 miles.

In 1964 SP and PTRA added CTC from Harrisburg Junction, TX to Deer Park Junction 7 miles. CTC was controlled by SP.

Also in 1964, SP extended CTC south from Sherman Jct., TX to Frisco Junction 2 miles. This was sold to BN in 1993.

In 1965 SP added CTC from Navasota Junction, TX to Bryan Junction 26 miles on the Dallas Div. Control was transferred to UP on Jan. 9, 1992.

In 1967 SP converted 1 mile of double track to single track and added CTC from Niles, TX to Chaney Junction on the San Antonio Div.

In 1973 and 1974 SP invested $22 million to added CTC from Sierra Blanca, TX to Flatonia 590 miles on San Antonio Div. It added 19 new sidings and upgraded 43 older sidings during the project. The work began at Flatonia and worked west. The first segment bewteen Flatonia and Kirby (San Antonio) 82 miles was completed in 1973. Work began on the second segment between Withers to Alpine Junction 380 miles in late 1973 and was completed in 1974. The third segment from Paisano to Sierra Blanca 117 miles was completed in November 1974. This was the biggest change to the signal system since the original semaphore signals were added back in the mid-1920s.

In 1980 SP added CTC from China, TX to Beaumont 10 miles on the Lafayette Div. and added CTC from Hearne, TX to Giddings 57 miles on the San Antonio Div.

The SP abandoned 140 miles of track in south Texas on January 1, 1980 when SP gained trackage rights over the Missouri Pacific from near Victoria to Harlingen.

In 1980 SSW added CTC Herington to Topeka 83 miles on former Rock Island including a major rebuild with welded rail and upgraded signals.

In 1982 SP added CTC from Dawes, TX to China 62 miles and from Tower 31 to Echo, TX 23 miles on the Lafayette Div.

In 1993 SP added CTC from Withers, TX to Tower 112 on 8 miles of double tracks in San Antonio.

In 1994 SP added CTC from Bremond, TX to Kosse 11 miles on the Dallas Div. and added CTC from Tower 17 to Eagle Lake, TX 35 miles on the San Antonio Div.

In 2000 UP added CTC between Eagle Lake, TX and Flatonia 50 miles and added CTC between Muldoon and Flatonia 8 miles.