The first trains departed for through service between Los Angeles and New Orleans on February 5, 1883.[3]
When Southern Pacific Railroad merged with Union Pacific in 1996, the operating plan that was filed along with the merger application stipulated that one of the first major investments would be to double-track the Sunset Route between Los Angeles, California and El Paso, Texas.[4] At the time of the merger, only about 152 miles (245 km), or approximately 20% of the route, were double-tracked.[5][6] However, the combined company's efforts to expand double-trackage between Los Angeles and El Paso were soon delayed in favor of more profitable investments on Union Pacific's pre-existing lines north of the Sunset Route to improve coal-hauling capacity or to better handle mixed-freight trains along the Central Corridor.[4]
Work to add the second mainline track picked up in the mid-2000s,[7][8] and by late 2007, Union Pacific was targeting the complete double-tracking of the 757-mile (1,218 km) Los Angeles-El Paso section by the end of 2010.[9][10] By 2012, 72% of that section, or 547 miles (880 km), would have two tracks, including the entire section between Tucson, Arizona and El Paso. Union Pacific no longer provided a specific timeline for full completion of the second mainline, though.[11] As of 2015[update], the double-tracking project reached 80% completion.[12] In 2024, Union Pacific announced the resumption of work to add the second mainline on the remaining 127 miles (204 km) of single-track railway.[13][14]
The line is primarily used for freight by the Union Pacific. BNSF shares ownership of the Lafayette Subdivision.[16] By 2007, 45 trains daily were operating through Maricopa, Arizona,[7] 55 daily trains were running in 2015, and 90 were projected after the full completion of the second mainline on the Los Angeles-El Paso section.[12] However, by 2019 the number of daily trains between Los Angeles and El Paso had dropped to 39, and the section east of El Paso in the Trans-Pecos region of West Texas was hosting 12 trains per day.[17]
