Denver and Rio Grande Western (also known as D&RGW) was a former railway of Southern Pacific Lines, which in turn purchased them in 1988. They operated in Colorado, Utah, and northern New Mexico. Rio Grande started out as a narrow gauge railway company, running rails south of Denver, Colo. Starting in 1870, Rio Grande ran a transcontinental line from Denver to Salt Lake City (now ran in standard gauge through the Moffat Tunnel). Rio Grande serviced coal and mineral traffic.

Rio Grande is most famous for servicing the Moffat Tunnel and the Royal Gorge routes, with labels on train cars saying "Scenic Line of the World". The Moffat Tunnel, the railroad pass between Colorado an Utah, is operated now by Union Pacific as a slip line for freight and passenger trains. The tunnel will occasionally also see trains operated by Burlington Northern Santa Fe and Amtrak.

Dates of operation: 1870-1988