24 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lowville | 1 | 4,856 | 4,871 | -0.21% | 128 | 38 | Town |
| Lowville | 2 | 3,320 | 3,337 | -0.09% | 1,750 | 2 | Village |
| Croghan | 3 | 3,193 | 3,193 | -0.09% | 18 | 179 | Town |
| New Bremen | 4 | 2,774 | 2,785 | -0.14% | 50 | 56 | Town |
| Denmark | 5 | 2,627 | 2,640 | -0.15% | 52 | 51 | Town |
| Watson | 6 | 1,782 | 1,793 | -0.11% | 16 | 114 | Town |
| West Turin | 7 | 1,681 | 1,683 | -0.06% | 16 | 103 | Town |
| Diana | 8 | 1,602 | 1,612 | -0.19% | 12 | 138 | Town |
| Leyden | 9 | 1,579 | 1,572 | -0.19% | 47 | 33 | Town |
| Martinsburg | 10 | 1,316 | 1,322 | -0.15% | 17 | 75 | Town |
| Greig | 11 | 1,183 | 1,184 | -0.25% | 13 | 93 | Town |
| Lyonsdale | 12 | 1,148 | 1,175 | -0.61% | 17 | 68 | Town |
| Turin | 13 | 756 | 763 | -0.4% | 24 | 31 | Town |
| Copenhagen | 14 | 659 | 663 | -0.15% | 558 | 1 | Village |
| Croghan | 15 | 636 | 640 | -0.16% | 1,489 | 0 | Village |
| Port Leyden | 16 | 594 | 594 | 0% | 892 | 1 | Village |
| Lyons Falls | 17 | 592 | 596 | -0.17% | 611 | 1 | Village |
| Harrisburg | 18 | 475 | 476 | -0.21% | 12 | 40 | Town |
| Castorland | 19 | 337 | 339 | 0% | 1,000 | 0 | Village |
| Pinckney | 20 | 311 | 313 | -0.32% | 8 | 41 | Town |
| Constableville | 21 | 303 | 300 | 0.33% | 268 | 1 | Village |
| Osceola | 22 | 242 | 243 | 0% | 3 | 88 | Town |
| Turin | 23 | 212 | 214 | 0% | 205 | 1 | Village |
| Montague | 24 | 95 | 95 | 0% | 1 | 64 | Town |
Lowville is the largest city in Lewis County, with a population of 4,856.
Montague is the smallest city in Lewis County, with a population of 95.
There are 24 cities in Lewis County, New York.