You are in the CarrTracks website Picture Gallery.
Construction on Southern Pacific's Sunset Route began from Los Angeles in 1873 and reached Colton in 1875. It reached Yuma, AZ in September 1877, Casa Grande in May 1879, Tucson in March 1880, and El Paso in May 1881. The Galveston, Harrisburg, & San Antonio building west from Houston reached San Antonio in 1877, then met the SP east of Sanderson near the Pecos River bridge on January 12, 1883. There were train order stations at Yuma, Wellton, Mohawk, Sentinel, Gila Bend, Estrella, Maricopa, Casa Grande, Picacho, Red Rock, Tucson, Mescal, Benson, Dragoon, Cochise, Willcox, Bowie, San Simon, Lordsburg, Separ, Deming, Cambray, Afton, Strauss, Anapra, and El Paso. The only record I can find for the installation of automatic block signals was when the SP added signals between Gila and Estrella in 1909. I'm pretty sure the rest of the line from Yuma to El Paso received semaphore signals around this same time frame.
When I first visited Tucson in March 1968 and spent several days recording freight train consists, the primary power was SD45s, GP35s, and U25Bs. A fairly common combination was two SD45s bracketed by a GP35 and a U25B. However, there were all kinds of other combinations plus the occasional U50, DD35B, GP30, and GP9. The Sunset Limited (the only surviving passenger train) was powered by an E9 and an E7B.
When I started taking pictures in the early 70s, the primary freight power on the Sunset Route was SD45s and U33Cs. The crews disliked the big GE U Boats as they rode rough. The big GEs didn't last long and were replaced by GP40s and Baby Boats in the early 80s.
For most of the route there were few improvements to the original route laid out by the SP in the 1880s. Sidings were lengthened to handle longer trains and there were two sections of double track. A second track was added between Wellton and Dome in 1926. With the merger of the El Paso and Southwestern into the SP in 1927 the two lines were tied together at Tucson and Mescal and used as double track between those points. The former SP line was used by eastbound trains and the EP&SW line was used by westbound trains. But for the most part, the Sunset Route was single track across Arizona and New Mexico. CTC was installed between Mescal and Lordsburg in 1958. During 1958 and 1959 CTC was added between Lordsburg and Anapra (end of double track just west of El Paso) and between Tucson and Gila Bend. In June 1960, the CTC installation was completed between Gila Bend and Yuma.
With the increase in container traffic, there were just too many trains for this congested single track line. SP management decided to remove track from Donner Pass and double track the problem areas on the Sunset Route. The problem areas were the grades around Benson. The SP began adding a second track between Fenner and Dragoon in 1994. This project was completed between Mescal and Dragoon in 1996. The Union Pacific continued the double track project extending the double track eastward from Dragoon to Cochise and adding a second track between Luzena and Raso in 2001. It added a second track between Stanwix and Sentinel in 2002 and Fortuna to Blaisdell in 2006. By August 2008 the whole route east of Tucson to El Paso was double track. Work had already started at Estrella and began working eastward completing double track to Mobile by the end of 2008 and Maricopa in 2009. At the same time the UP plans to add a small classification yard at Red Rock to handle traffic in and out of Phoenix. The ultimate goal is double track form Colton to El Paso.
This gallery does include the Santa Fe Branch from Rincon, NM to Deming. This link formed the second transcontinental railroad system across the US. As reference, I've added timetables from the Gila and Lordsburg Subdivisions.
Santa Fe at Deming