Colusa is a small, lightly populated county at the northern portion of the Central Valley. Although its western marging reaches into the Coast Range with areas of chaparral and oak woodland, the vast majority of Colusa County is valley bottomland, most of which is devoted to agriculture. There are also several large wildlife refuges in the county that attract tens of thousands of waterfowl every winter. The Sacramento River runs through the town of Colusa and along its banks are extensive strips of riparian woodland.