The Rio Grande Southern Railroad (reporting mark RGS, also referred to as The Southern) was a 3 ft (914 mm) narrow-gauge railroad which ran in the southwestern region of the US state of Colorado, from the towns of Durango to Ridgway, routed via Lizard Head Pass. Built by Russian immigrant and Colorado toll road builder Otto Mears, the RGS operated from 1891 through 1951 and was built with the intent to transport immense amounts of silver mineral traffic that were being produced by the mining communities of Rico and Telluride. On both ends of the railroad, there were interchanges with The Denver and Rio Grande Railroad (reporting mark D&RG(W), later known as the Denver and Rio Grande Western), which would ship the traffic the RGS hauled elsewhere like the San Juan Smelter in Durango.