High Quality Content by WIKIPEDIA articles! Stillwater is a city in Washington County, Minnesota, directly across the St. Croix River from the state of Wisconsin. The population was 15,143 at the 2000 census. It is the county seat of Washington County. Stillwater is part of the Twin Cities Metro Area.Stillwater is notable for its antiquarian bookstores, being a book town. According to the United States Census Bureau, the city has a total area of 7.3 square miles (18.9 km²), of which, 6.5 square miles (16.8 km²) of it is land and 0.8 square miles (2.1 km²) of it (11.37%) is water. State Highways 36, 95, and 96 are three of the main routes in the community.