The name traces its origins to the Galveston, Harrisburg and San Antonio Railway, a Southern Pacific Railway subsidiary which was known as the Sunset Route as early as 1874.[citation needed] The line was built by several different companies and largely consolidated under Southern Pacific.
Upon Southern Pacific Railroad's merger with Union Pacific in 1996, less than 25% of the route was double-tracked.[2] Efforts to expand double-trackage were ongoing as of the late 2000s and early 2010s,[3] with over seventy percent of the route having two tracks by 2012.[2]
The line is primarily used for freight by the Union Pacific. BNSF shares ownership of the Lafayette Subdivision.[4] By 2007, 45 trains daily were operating through Maricopa, Arizona.[3] The AmtrakSunset Limited operates three round-trips weekly over the entirety of the route with the Texas Eagle attached between San Antonio and Los Angeles.
