[3] In-house production was chosen to preemptively address material shortages and personnel issues (any possible labor unrest could be more easily controlled by the D&RGW).

The locos also worked out of Alamosa, Colorado to Antonito over Cumbres Pass to Chama and on to Durango and the Farmington branch.

491, 493 and 499, were equipped with steam heat and signal lines so they could haul passenger trains like the San Juan Express and Shavano.

The D&RGW operated #491 from 1928 to 1963, but in 1947 it added thermic siphons to improve efficiency by increasing heating surface area in the firebox.

The Durango & Silverton originally owned four of the surviving K-37s, but they found that the #497 was too hard on their track and did not handle the Animas Canyon section of the route as well as they would have hoped.

However, the problems experienced by the Durango & Silverton were due to mechanical complications with #497's trailing truck caused by a 1960 wreck, and not universal to all K-37s.

[7] On January 24, 2020, #493 moved under its own power for the first time in over 50 years, making it the first D&RGW K-37 class since #497 to run on the D&SNG.