Chris nailed the location.

I have a friend, Charles Mutschler, look at the video and share his thoughts. He grew up in Durango and is quite familiar with the D&RGW narrow gauge. Here is his detailed report:

Looks like a compilation of film taken at round ups by the ranchers in the Powderhorn Mesa area west and south of Gunnison, Colorado. Most of the cattle loading scenes appear to be Gunnison. The stock yards were at the southwest side of the D&RGW yards, and you can see the coal tipple in the distance in one scene. The false front buildings look like Iola, a very small town west of Gunnison which had a very small stock yard, and some cattle were loaded there, though most of the big shipments came out of Gunnison, Parlins, or Sargent. The opening scenes of cattle being trail driven appear to be partially on the Powderhorn Mesa area, where there is little vegetation except sagebrush, and the scene with the trees and lake may be along the Lake Fork of the Gunnison, between Sapinero and Lake City. The Lake Fork was the valley once served by the Lake City Branch, built in the expectation of mining prosperity, and abandoned in the 1930s with little traffic on the single combine which was the usual consist of the daily mixed train beyond an occasional case of groceries and the odd traveling salesman who made a mistake in his itinerary.

Someone may be able to identify the vehicles and give a better date estimate. Clearly post WWII - the flying Rio Grande herald on the equipment was first applied in November, 1939, but wasn't ubiquitous for several years. The last stock extras ran in the fall of 1953, and the railroad petitioned for abandonment west of Poncha Junction.

We spent several summers in the Gunnison country when my father was doing field work in the mountains around Crested Butte. Nice to see this. I wonder what other footage may be out
there?