DRGW 491 was rebuilt in 1930 at the Burnham Shops in Denver (now extinct) and converted from a 4 foot to a 3 foot gauge configuration. Designated K-37 class, the unique frame configuration had the driving wheels placed between the two chassis frames which support the boiler, but with the cylinders, driving rods, counterweights and valve gear located on the outside the frame. The K-37's were the largest operating narrow gauge steam locomotives in the Western US and worked in numerous mountain areas in Colorado including Salida, Gunnison, Crested Butte, Alamosa and even the Cumbres Pass to Chama. Of the 10 K-37 locomotives built 8 still exist, with DRGW 491 carrying the flag for those that cannot run.
