1. Home
 ›
2. Fallen Flags
 ›
3. Denver & Rio Grande Western
 ›
4. 4-6-6-4

Rio Grande 4-6-6-4 Locomotives: Specs, Roster, Photos

Published: April 10, 2025

The Rio Grande was always after large and powerful locomotives to handle heavy freights through the rugged Colorado Rockies, in particular with its ever-constant battle of Tennessee Pass.  It utilized wheel arrangements such as the 2-8-8-2, 2-6-6-2, 2-10-2, 4-8-2, and 4-8-4.

The railroad acquired its first examples of the 4-6-6-4 in 1938 from Baldwin and later picked up more a few years later.  The company's intent was to speed up freight trains, and in this capacity the engines thrived as designed.

Interestingly, in an effort to meet wartime demands, the railroad acquired even more that had originally been ordered by Union Pacific.   While the D&RGW was never pleased with these final examples - and ultimately only leased by the railroad - the earlier examples remained in service until the early 1950s.

One of the Denver & Rio Grande Western's big 4-6-6-4's, #3713 (Class L-105), is seen here in Salt Lake City, Utah circa 1950. Stephen Bogen photo.

Rio Grande 4-6-6-4 #3710 (L-105) departs Denver for Pueblo, Colorado during 1952. Robert Le Massena photo.