The K-27 is a 3 foot narrow-gauge Mikado Class 2-8-2 steam locomotive built for the Denver and Rio Grande Railroad by the Baldwin Locomotive Works in 1903. Fifteen locomotives of this type were built, originally referred to as the class 125, but were re-classified as k-27's in 1924 when the Denver and Rio Grande became the Denver and Rio Grande Western. They eventually became known by the nickname "Mudhen" due to a waddling motion they had as they moved on the track.

The K-27's pulled freight, passenger and mixed trains on the D&RGW over the Rocky Mountains in Colorado, traversing the entire length of the railroad.

One K-27 of note is number 463, which was sold to cowboy actor and singer Gene Autry in May 1955. Autry never used the Mudhen and donated it to the City of San Antonio in 1970 for use on the Cumbres & Toltec Scenic Railway. After extensive rebuilding and restoration work was completed in 1994, number 463 was under steam again and served reliably on the Cumbres & Toltec until she was taken out of service due to a side rod breakage in 2002.

The other K-27 in existence is 464 which serves on the huckleberry railroad in flint, Michigan, after a short serve on Knotts Berry Farm.

locomotives 455,and 461 served on the rio grande southern railroad until 1951 when the railroad was scrapped.