Washington County, Kansas is located south of the Kansas-Nebraska border and east of the 6th Principal Meridian. U.S. Highway 36 runs east and west across the county and State Highway 15 runs north and south.

Washington County is made up of twelve cities/villages; Barnes, Clifton, Greenleaf, Haddam, Hanover, Hollenberg, Linn, Mahaska, Morrowville, Palmer, Vining, and Washington, which is the county seat. There are twenty-five (25) townships in the 30 miles by 30 miles that comprise the county.