No other animal played as important a role in the early history and exploration of this country as did the beaver. This is particularly true of the Rocky Mountain west, and to a lesser extent of the Northwest. The fur trade made the beaver pelt a standard of exchange, and to get beaver the trappers moved westward, seeking out this valuable animal in the most inaccessible and remote regions. These early explorations, which had as their incentive fur rather than the expansion of territory, paved the way for later settlement by those seeking new lands and a better livelihood in the West. So great was the demand for fur that the beavers, in the beginning abundant, were reduced in numbers to a point where returns did not compensate trappers for the risk and hardship involved. The first mention of beaver in the park is found in _Mammals and Birds of Mount Rainier_, Taylor and Shaw, which states: “Dr. A. K. Fisher records that several beavers lived at Longmire Springs until 1896, when a trapper killed them all.” By 1905, according to the _Annual Report of the Secretary of the Interior_, beaver had been exterminated within the boundaries of the park. However, by 1919, beaver were again active on Fish Creek, along the eastern base of Mount Wow, and in December, Mr. Roger W. Toll, park superintendent, reported two dams, each 100 to 200 feet in length. Mr. Toll’s observations were set forth thus in a letter: “The beavers are now living in these lakes, and fresh signs are abundant. There are numerous tracks in the snow leading from the lakes to the thickets of alder, elder, and willow which they are eating. There is no typical beaver house in the lakes, but the under-water entrance to their house can be seen leading under the roots of a fir tree about four feet in diameter that stands on the edge of the upper lake.” It is in this immediate vicinity that fairly extensive beaver workings were observed in November, 1947, including newly repaired small dams and fresh cuttings. The house or burrow in the stream bank studied by Mr. Toll appears typical of the beaver in this area. In other sections, notably Rocky Mountain National Park, Colorado, where beavers are abundant, an extensive system of dams and canals is frequently developed on the smaller streams, with a large house completely surrounded by the impounded water a central feature of the colony. No such elaborate workings have been found here. Since the beavers habitually reside in burrows along the margins of streams they are referred to as “bank-beavers.” A plausible explanation for this habit is the constant and ample flow of water, which eliminates the necessity for large dams, and is adequate to cover at all times the underwater entrances to the burrows.