45 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Washington | 1 | 3,530 | 3,530 | 0.09% | 61 | 58 | Township |
| Washington | 2 | 2,992 | 2,912 | 0.61% | 91 | 33 | Township |
| Washington | 3 | 1,078 | 1,069 | 0.19% | 1,109 | 1 | City |
| Hanover | 4 | 947 | 936 | 0.21% | 27 | 36 | Township |
| Hanover | 5 | 698 | 692 | 0.14% | 1,165 | 1 | City |
| Linn | 6 | 519 | 515 | 0.19% | 14 | 36 | Township |
| Clifton | 7 | 458 | 452 | 0.22% | 1,123 | 0 | City |
| Washington | 8 | 443 | 469 | -1.12% | 10 | 45 | Township |
| Greenleaf | 9 | 440 | 435 | 0.23% | 12 | 36 | Township |
| Linn | 10 | 390 | 387 | 0.26% | 1,150 | 0 | City |
| Washington | 11 | 383 | 397 | -0.26% | 11 | 36 | Township |
| Clifton | 12 | 379 | 365 | 0.8% | 11 | 36 | Township |
| Greenleaf | 13 | 352 | 349 | 0.28% | 779 | 0 | City |
| Clifton | 14 | 325 | 330 | 0% | 9 | 36 | Township |
| Washington | 15 | 317 | 307 | 0.63% | 9 | 35 | Township |
| Sherman | 16 | 268 | 262 | 0.75% | 7 | 36 | Township |
| Barnes | 17 | 222 | 222 | -0.45% | 6 | 36 | Township |
| Mill Creek | 18 | 184 | 181 | 0.55% | 5 | 36 | Township |
| Farmington | 19 | 176 | 174 | 0.57% | 5 | 36 | Township |
| Washington | 20 | 171 | 171 | 0% | 5 | 35 | Township |
| Haddam | 21 | 166 | 163 | 0.61% | 5 | 36 | Township |
| Barnes | 22 | 163 | 163 | 0% | 959 | 0 | City |
| Washington | 23 | 147 | 148 | 0% | 4 | 36 | Township |
| Palmer | 24 | 127 | 124 | 0.79% | 411 | 0 | City |
| Morrowville | 25 | 116 | 116 | 0% | 811 | 0 | City |
| Strawberry | 26 | 112 | 108 | 0.9% | 3 | 36 | Township |
| Haddam | 27 | 108 | 108 | 0% | 315 | 0 | City |
| Sheridan | 28 | 104 | 103 | 0% | 3 | 36 | Township |
| Washington | 29 | 76 | 71 | 1.33% | 1 | 57 | Township |
| Little Blue | 30 | 76 | 75 | 0% | 2 | 36 | Township |
| Brantford | 31 | 74 | 73 | 0% | 2 | 36 | Township |
| Washington | 32 | 65 | 68 | -1.52% | 1 | 47 | Township |
| Charleston | 33 | 65 | 64 | 0% | 2 | 35 | Township |
| Washington | 34 | 63 | 64 | 0% | 1 | 54 | Township |
| Coleman | 35 | 62 | 61 | 0% | 2 | 36 | Township |
| Union | 36 | 61 | 61 | 0% | 2 | 36 | Township |
| Washington | 37 | 59 | 59 | 0% | 2 | 36 | Township |
| Washington | 38 | 57 | 57 | 0% | 2 | 36 | Township |
| Kimeo | 39 | 52 | 49 | 1.96% | 1 | 36 | Township |
| Hanover | 40 | 49 | 49 | 0% | 1 | 36 | Township |
| Lowe | 41 | 49 | 46 | 2.08% | 1 | 35 | Township |
| Grant | 42 | 48 | 45 | 2.13% | 1 | 36 | Township |
| Washington | 43 | 45 | 45 | 0% | 1 | 36 | Township |
| Mahaska | 44 | 44 | 44 | 0% | 197 | 0 | City |
| Hollenberg | 45 | 12 | 12 | 0% | 164 | 0 | City |
Washington is the largest city in Washington County, with a population of 3,530.
Hollenberg is the smallest city in Washington County, with a population of 12.
There are 45 cities in Washington County, Kansas.