The American beaver was, at one time, numerous in the Rocky Mountains and at many points in the north. The great value of the fur has greatly lessened this fine fur-bearing animal. In many parts of the Rockies and in the north, geographic names indicate the abundance of the animal, such as Beaver creek, Beaver dam, etc. The presence of the beaver is often indicated by arms built, many of them long ago, and the impounding of water in the form of little lakes. A fine series of these was observed by the writer last summer on the Grand River beyond Ouray. Another small series was observed by the writer on Spruce creek, a tributary of the west fork of St. Louis creek, just above the summer camp of the Ames Foresters near the ranger station, at an altitude of about 9,200 feet.
Pammel, L. H.
"The Plants Found in a Beaver Swamp,"
Ames Forester: Vol. 6
, Article 14.
Available at: http://lib.dr.iastate.edu/amesforester/vol6/iss1/14