Though the narrow gauge steam in Salida outlasted them, the 3700 series 4-6-6-4's, which were originally assigned to the line between Grand Junction and Helper spent their last years operating south out of Denver to Pueblo, and some did work west from Pueblo, presumably to Salida or Minturn. A few of the 3700's lasted until February of 1956. When diesels became available, the line from Grand Junction to Helper was one of the first to be fully dieselized, in large part because the water supplies for steam engines on the Utah desert were of such poor water quality. That conversion released those 3700 series locomotives for use out of Denver and Pueblo. Of course, basing locomotives out of Pueblo was convenient for scrapping, as the locomotives could literally be run under steam to the scrapping yard.
A note about the 3600's mentioned elsewhere in this thread. A work associate of mine from a few years ago had a grandfather that was a steam locomotive engineer for the D&RGW out of Pueblo. During the last use of the 3600's in 1956, he was temporarily assigned to run the 3600's out of Tabernash as helpers through the Moffat Tunnel to East Portal. This work associate of mine, who was a young lady of 10 or 11 in 1956--and somewhat of a tomboy, asked if she could ride with her grandfather on a run with one of the 3600's. She got her wish and rode with him through the Moffat Tunnel on a 3600 series run as a rear helper by her Grandfather. She vividly recounted the ride to me a few years ago, remembering most vividly having to wear a gas mask (as did her Grandfather and the fireman) going through Moffat Tunnel. She also recounted that the smoke was so thick that it was impossible to see anything, even the cab gauges, while in the tunnel. I'm sure many railfans would give their eye teeth to have had her experience. She was no railfan, but she remembered always what a 3600 was.
