| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lowville | 1 | 4,863 | 4,887 | -0.12% | 128 | 38 | Town |
| Lowville | 2 | 3,304 | 3,335 | -0.15% | 1,742 | 2 | Village |
| Croghan | 3 | 3,172 | 3,189 | -0.19% | 18 | 179 | Town |
| New Bremen | 4 | 2,784 | 2,790 | -0.07% | 50 | 56 | Town |
| Denmark | 5 | 2,615 | 2,631 | -0.15% | 52 | 51 | Town |
| Watson | 6 | 1,765 | 1,774 | -0.11% | 15 | 114 | Town |
| West Turin | 7 | 1,678 | 1,690 | -0.12% | 16 | 103 | Town |
| Diana | 8 | 1,604 | 1,613 | -0.19% | 12 | 138 | Town |
| Leyden | 9 | 1,587 | 1,576 | 0.13% | 48 | 33 | Town |
| Martinsburg | 10 | 1,317 | 1,322 | -0.08% | 17 | 75 | Town |
| Greig | 11 | 1,194 | 1,190 | -0.08% | 13 | 93 | Town |
| Lyonsdale | 12 | 1,147 | 1,172 | -0.35% | 17 | 68 | Town |
| Turin | 13 | 758 | 764 | -0.26% | 24 | 31 | Town |
| Copenhagen | 14 | 658 | 663 | -0.15% | 558 | 1 | Village |
| Croghan | 15 | 631 | 637 | -0.16% | 1,478 | 0 | Village |
| Port Leyden | 16 | 587 | 590 | -0.17% | 881 | 1 | Village |
| Lyons Falls | 17 | 586 | 590 | -0.17% | 605 | 1 | Village |
| Harrisburg | 18 | 483 | 484 | 0% | 12 | 40 | Town |
| Castorland | 19 | 341 | 340 | 0% | 1,012 | 0 | Village |
| Pinckney | 20 | 313 | 313 | 0% | 8.0 | 41 | Town |
| Constableville | 21 | 302 | 305 | -0.33% | 267 | 1 | Village |
| Osceola | 22 | 243 | 244 | 0% | 3.0 | 88 | Town |
| Turin | 23 | 213 | 215 | -0.47% | 206 | 1 | Village |
| Montague | 24 | 91 | 91 | 0% | 1.0 | 64 | Town |
Lowville is the largest city in Lewis County, with a population of 4,863.
Montague is the smallest city in Lewis County, with a population of 91.
There are 24 cities in Lewis County, New York.