I have found beaver living in Kansas and also in the lower Colorado River. In neither of these places do they build houses. The banks are soil and burrows are easily dug. In Colorado I found houses, but the locality was very rocky and burrows would be difficult to dig. Around three lakes, houses seems to be of two classes. In one case the houses are in low land that did not rise sufficiently above the permanent water level to give room for case burrows, so houses were built to cover dry sleeping quarters. In the other case partial houses were built against banks of rocky ground when the beavers could not burrow deep enough to be safe, and the entrance of short burrows was covered by larger or smaller stick piles. One or two of this last type of house was on the lake shore, and one is just within the rapids at the outlet of Hassilborg Lake where the water could not freeze over, and beavers could get to the dry land all winter. The dams were manually very irregular in shape, as if they were evolved about to take advantage of any local help in the way of snarrows or trees.