West Mountain is a census-designated place (CDP) in the town of Ridgefield, Connecticut, United States. As of the 2020 census, West Mountain had a population of 603. It is on the west side of Ridgefield and is bordered to the west by the towns of North Salem and Lewisboro in Westchester County, New York. The West Mountain Historic District occupies 425 acres (172 ha) at the center of the CDP, and newer residences occupy portions of the remainder of the CDP.