24 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lowville | 1 | 4,875 | 4,873 | -0.06% | 129 | 38 | Town |
| Lowville | 2 | 3,335 | 3,338 | -0.03% | 1,758 | 2 | Village |
| Croghan | 3 | 3,209 | 3,191 | 0.09% | 18 | 179 | Town |
| New Bremen | 4 | 2,779 | 2,784 | -0.07% | 50 | 56 | Town |
| Denmark | 5 | 2,632 | 2,638 | -0.08% | 52 | 51 | Town |
| Watson | 6 | 1,790 | 1,793 | 0% | 16 | 114 | Town |
| West Turin | 7 | 1,689 | 1,688 | 0.06% | 16 | 103 | Town |
| Diana | 8 | 1,608 | 1,611 | -0.12% | 12 | 138 | Town |
| Leyden | 9 | 1,581 | 1,570 | -0.06% | 47 | 33 | Town |
| Martinsburg | 10 | 1,320 | 1,319 | 0% | 18 | 75 | Town |
| Greig | 11 | 1,189 | 1,185 | -0.17% | 13 | 93 | Town |
| Lyonsdale | 12 | 1,155 | 1,172 | -0.35% | 17 | 68 | Town |
| Turin | 13 | 764 | 764 | 0% | 24 | 31 | Town |
| Copenhagen | 14 | 659 | 662 | -0.15% | 558 | 1 | Village |
| Croghan | 15 | 640 | 639 | 0% | 1,499 | 0 | Village |
| Lyons Falls | 16 | 596 | 595 | 0% | 615 | 1 | Village |
| Port Leyden | 17 | 591 | 591 | 0% | 887 | 1 | Village |
| Harrisburg | 18 | 481 | 478 | 0% | 12 | 40 | Town |
| Castorland | 19 | 340 | 338 | 0% | 1,009 | 0 | Village |
| Pinckney | 20 | 312 | 312 | -0.32% | 8 | 41 | Town |
| Constableville | 21 | 302 | 302 | 0% | 267 | 1 | Village |
| Osceola | 22 | 242 | 243 | 0% | 3 | 88 | Town |
| Turin | 23 | 214 | 214 | 0% | 207 | 1 | Village |
| Montague | 24 | 96 | 96 | 0% | 2 | 64 | Town |
Lowville is the largest city in Lewis County, with a population of 4,875.
Montague is the smallest city in Lewis County, with a population of 96.
There are 24 cities in Lewis County, New York.