Stilwell is a city and county seat of Adair County, Oklahoma, United States. The population was 3,949 at the 2010, an increase of 20.5 percent from 3,276 at the 2000 census. In 1949, the Oklahoma governor and legislature proclaimed Stilwell as the "Strawberry Capital of the World." Stilwell also serves as a gateway to Lake Tenkiller and the former Adair State Park.