Founded in 1857, Washington County is one of 105 counties in the state of Kansas. Historically, Washington County was formed from unorganized area. The city of Washington is the county seat. With FIPS code of 201, Washington County has a population of 5,511 and area of 898 square miles (2,326 km2).
List of all cities in Washington County, KS alphabetically
| City/Town | Postal Code | Area Code |
| Barnes, KS | 66933 | 785 |
| Clifton, KS | 66937 | 785 |
| Greenleaf, KS | 66943 | 785 |
| Haddam, KS | 66944 | 785 |
| Hanover, KS | 66945 | 785 |
| Hollenberg, KS | 66946 | 785 |
| Linn, KS | 66953 | 785 |
| Mahaska, KS | 66955 | 785 |
| Morrowville, KS | 66958 | 785 |
| Palmer, KS | 66962 | 785 |
| Washington, KS | 66968 | 785 |