55 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Potsdam | 1 | 14,304 | 14,934 | -1.47% | 141 | 101 | Town |
| Massena | 2 | 12,069 | 12,416 | -0.83% | 272 | 44 | Town |
| Canton | 3 | 11,187 | 11,801 | -1.17% | 107 | 105 | Town |
| Massena | 4 | 9,935 | 10,249 | -0.63% | 2,193 | 5 | Village |
| Ogdensburg | 5 | 9,135 | 9,870 | -1.58% | 1,843 | 5 | City |
| Potsdam | 6 | 8,078 | 8,498 | -1.03% | 1,643 | 5 | Village |
| Canton | 7 | 6,848 | 7,391 | -1.57% | 1,652 | 4 | Village |
| Gouverneur | 8 | 6,574 | 6,490 | 0.47% | 92 | 71 | Town |
| Norfolk | 9 | 4,327 | 4,452 | -0.48% | 76 | 57 | Town |
| Lisbon | 10 | 4,266 | 4,219 | 0.21% | 39 | 108 | Town |
| Oswegatchie | 11 | 3,945 | 4,141 | -0.33% | 60 | 65 | Town |
| Stockholm | 12 | 3,881 | 3,819 | 0.57% | 41 | 94 | Town |
| Gouverneur | 13 | 3,579 | 3,618 | -0.22% | 1,633 | 2 | Village |
| Louisville | 14 | 2,967 | 3,042 | -0.5% | 61 | 49 | Town |
| Brasher | 15 | 2,565 | 2,620 | -0.16% | 28 | 91 | Town |
| Pierrepont | 16 | 2,540 | 2,515 | 0.24% | 42 | 60 | Town |
| De Kalb | 17 | 2,347 | 2,369 | 0.21% | 28 | 83 | Town |
| Waddington | 18 | 2,224 | 2,225 | 0% | 43 | 52 | Town |
| Fowler | 19 | 2,145 | 2,135 | 0.05% | 36 | 59 | Town |
| Morristown | 20 | 2,066 | 2,077 | 0.1% | 45 | 46 | Town |
| Parishville | 21 | 1,978 | 2,026 | -0.55% | 20 | 98 | Town |
| Russell | 22 | 1,842 | 1,866 | -0.65% | 19 | 97 | Town |
| Madrid | 23 | 1,698 | 1,738 | -0.7% | 32 | 53 | Town |
| Norwood | 24 | 1,524 | 1,569 | -0.59% | 727 | 2 | Village |
| Colton | 25 | 1,484 | 1,522 | -0.47% | 6 | 242 | Town |
| Fine | 26 | 1,272 | 1,305 | -0.55% | 8 | 167 | Town |
| Hammond | 27 | 1,244 | 1,261 | -0.56% | 20 | 62 | Town |
| Hermon | 28 | 1,104 | 1,076 | 0.45% | 21 | 53 | Town |
| Hopkinton | 29 | 1,076 | 1,102 | -0.46% | 6 | 185 | Town |
| De Peyster | 30 | 1,061 | 1,017 | 0.66% | 25 | 43 | Town |
| Edwards | 31 | 983 | 1,011 | -0.81% | 20 | 50 | Town |
| Macomb | 32 | 934 | 918 | -0.64% | 15 | 61 | Town |
| Waddington | 33 | 925 | 930 | -0.11% | 424 | 2 | Village |
| Hannawa Falls | 34 | 854 | 1,040 | -1.5% | 167 | 5 | CDP |
| Madrid | 35 | 838 | 805 | 0.6% | 225 | 4 | CDP |
| Pitcairn | 36 | 794 | 792 | 0% | 14 | 59 | Town |
| Rossie | 37 | 770 | 795 | -0.77% | 20 | 38 | Town |
| Norfolk | 38 | 755 | 886 | -4.79% | 279 | 3 | CDP |
| Heuvelton | 39 | 705 | 714 | -0.28% | 926 | 1 | Village |
| DeKalb Junction | 40 | 676 | 535 | 1.5% | 170 | 4 | CDP |
| Edwards | 41 | 675 | 430 | 7.14% | 730 | 1 | CDP |
| Clifton | 42 | 675 | 678 | -0.15% | 5 | 134 | Town |
| Parishville | 43 | 647 | 623 | 0% | 196 | 3 | CDP |
| Hailesboro | 44 | 628 | 776 | 0% | 134 | 5 | CDP |
| Star Lake | 45 | 609 | 540 | -2.09% | 140 | 4 | CDP |
| Hermon | 46 | 596 | 387 | 7.19% | 1,211 | 0 | CDP |
| Brasher Falls | 47 | 470 | 605 | -2.89% | 286 | 2 | CDP |
| Rensselaer Falls | 48 | 319 | 318 | 0% | 1,096 | 0 | Village |
| Hammond | 49 | 281 | 285 | -0.35% | 480 | 1 | Village |
| Piercefield | 50 | 272 | 282 | -0.73% | 3 | 104 | Town |
| Richville | 51 | 257 | 266 | -0.77% | 348 | 1 | Village |
| Colton | 52 | 256 | 290 | -2.29% | 154 | 2 | CDP |
| Winthrop | 53 | 166 | 174 | -12.17% | 60 | 3 | CDP |
| Cranberry Lake | 54 | 105 | 126 | -5.41% | 5 | 19 | CDP |
| Clare | 55 | 92 | 96 | -1.08% | 1 | 96 | Town |
Potsdam is the largest city in St. Lawrence County, with a population of 14,304.
Clare is the smallest city in St. Lawrence County, with a population of 92.
There are 55 cities in St. Lawrence County, New York.