| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Washington | 1 | 1,063 | 1,068 | 0% | 1,094 | 1 | City |
| Hanover | 2 | 689 | 695 | -0.14% | 1,150 | 1 | City |
| Clifton | 3 | 458 | 452 | 0.22% | 1,123 | 0 | City |
| Linn | 4 | 386 | 387 | 0% | 1,139 | 0 | City |
| Greenleaf | 5 | 354 | 355 | 0% | 783 | 0 | City |
| Barnes | 6 | 161 | 163 | -0.62% | 947 | 0 | City |
| Palmer | 7 | 126 | 127 | 0% | 408 | 0 | City |
| Morrowville | 8 | 112 | 114 | -0.88% | 783 | 0 | City |
| Haddam | 9 | 107 | 109 | -0.93% | 312 | 0 | City |
| Mahaska | 10 | 42 | 44 | -2.33% | 188 | 0 | City |
| Hollenberg | 11 | 13 | 13 | 0% | 178 | 0 | City |
Washington is the largest city in Washington County, with a population of 1,063.
Hollenberg is the smallest city in Washington County, with a population of 13.
There are 11 cities in Washington County, Kansas.