The oldest predecessor of today’s SLRG was the Denver and Rio Grande Railroad (D&RG), which was chartered in 1870. The line over La Veta Pass to Alamosa and Antonito was originally envisioned as part of an ambitious and never-realized narrow gauge (three feet between the rails) line linking Denver with Mexico City. The narrow gauge tracks crossed the pass in 1877 and reached Alamosa on July 6, 1878. The railroad was pushed on to Antonito by 1880 and ultimately to Santa Fe, New Mexico and Silverton, Colorado. The D&RG built west from Alamosa, completing the line to South Fork and its terminus at Creede in 1881.

By the late 1880s, the inherent isolation of narrow gauge railroads from the national network began to put them at a competitive disadvantage. The D&RG converted the La Veta Pass and the Creede lines to standard gauge around 1900. The line to Antonito was also converted to standard gauge, but a third rail, laid to three-foot gauge, remained to Alamosa until the end of regular narrow gauge operation in 1968. Coincident with the conversion to standard gauge, the D&RG realigned the route over La Veta Pass to lower the summit, straighten curves and reduce grades.

In 1908, the D&RG was consolidated with the Rio Grande Western to form the Denver and Rio Grande Western (DRGW). In 1988, the DRGW purchased the giant Southern Pacific Railroad (SP). The combined companies were named for the larger and wider-reaching company, the SP. Union Pacific Railroad (UP) purchased and merged the SP in 1996. On June 29, 2003, the UP sold the Walsenburg - Alamosa, Alamosa – Antonito and Alamosa – Derrick (just west of South Fork) to shortline railroad conglomerate RailAmerica (RA). The Derrick – Creede line, which had been out of service, was sold to the Denver and Rio Grande Historical Foundation as a tourist line. RA sold the SLRG to Permian Basin Railways on December 22, 2005.

The SP-1744 is a fully-restored, 2-6-0 Mogul steam locomotive built by Baldwin Locomotive Works of Philadelphia for the Southern Pacific Railroad. The engine was commissioned into regular service in 1901. This enigne served a variety of roles throughout the first half of the 20th century, with her primary roots in the central valleys of California before retiring from general service in the mid-1950s. A few years later, she was brought back into the limelight when she became a one-time classic film star, starring alongside Rock Hudson on the silver screen in “The Earth is Mine.”Later, she was acquired by railroads in Utah and then Texas, then New Orleans before being acquired by the Rio Grande Scenic Railroad.

The LS&I-18 is a fully-restored, 2-8-0 Consolidation steam locomotive built by the American Locomotive Company at its Pittsburgh works in 1910. The LS&I, or Lake Superior and Ishpeming, was a northern Michigan railroad that primarily hauled iron ore, and when they were built, the C-5 Consolidations were the most powerful locomotives on the roster.After the LS&I converted to diesel in the 1950’s, the 18 was stored. Later, itt was sold to the Marquette and Huron Mountain tourist line, then to the Grand Canyon Railroad. In early 2007 it was sold to Fleming Locomotive Works and operated in Oregon on the Mount Hood Railroad. Rio Grande Scenic Railroad acquired the 18 in late 2007.