Washington County is located in Southeast Iowa and covers 556.75 square miles in the richest of America's agricultural region. The population of the county was 21,704 people according to the 2010 census. The nine incorporated cities in the county are Ainsworth, Brighton, Coppock, Crawfordsville, Kalona, Riverside, Washington, Wellman, and West Chester. Washington City is the county seat of Washington County and county business has been conducted at the courthouse, 222 West Main Street, since 1887.