42 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Potsdam | 1 | 14,090 | 14,934 | -1.5% | 139 | 101 | Town |
| Massena | 2 | 11,968 | 12,416 | -0.84% | 270 | 44 | Town |
| Canton | 3 | 11,054 | 11,801 | -1.19% | 106 | 105 | Town |
| Massena | 4 | 9,872 | 10,249 | -0.63% | 2,179 | 5 | Village |
| Ogdensburg | 5 | 8,988 | 9,870 | -1.61% | 1,814 | 5 | City |
| Potsdam | 6 | 7,994 | 8,498 | -1.04% | 1,625 | 5 | Village |
| Canton | 7 | 6,740 | 7,391 | -1.58% | 1,626 | 4 | Village |
| Gouverneur | 8 | 6,605 | 6,490 | 0.47% | 93 | 71 | Town |
| Norfolk | 9 | 4,306 | 4,452 | -0.49% | 76 | 57 | Town |
| Lisbon | 10 | 4,275 | 4,219 | 0.21% | 39 | 108 | Town |
| Oswegatchie | 11 | 3,932 | 4,141 | -0.33% | 60 | 65 | Town |
| Stockholm | 12 | 3,903 | 3,819 | 0.57% | 42 | 94 | Town |
| Gouverneur | 13 | 3,571 | 3,618 | -0.22% | 1,629 | 2 | Village |
| Louisville | 14 | 2,952 | 3,042 | -0.51% | 61 | 49 | Town |
| Brasher | 15 | 2,561 | 2,620 | -0.16% | 28 | 91 | Town |
| Pierrepont | 16 | 2,546 | 2,515 | 0.24% | 42 | 60 | Town |
| De Kalb | 17 | 2,352 | 2,369 | 0.21% | 29 | 83 | Town |
| Waddington | 18 | 2,224 | 2,225 | 0% | 43 | 52 | Town |
| Fowler | 19 | 2,146 | 2,135 | 0.05% | 36 | 59 | Town |
| Morristown | 20 | 2,068 | 2,077 | 0.1% | 45 | 46 | Town |
| Parishville | 21 | 1,967 | 2,026 | -0.56% | 20 | 98 | Town |
| Russell | 22 | 1,830 | 1,866 | -0.65% | 19 | 97 | Town |
| Madrid | 23 | 1,686 | 1,738 | -0.71% | 32 | 53 | Town |
| Norwood | 24 | 1,515 | 1,569 | -0.59% | 723 | 2 | Village |
| Colton | 25 | 1,477 | 1,522 | -0.47% | 6 | 242 | Town |
| Fine | 26 | 1,265 | 1,305 | -0.55% | 8 | 167 | Town |
| Hammond | 27 | 1,237 | 1,261 | -0.56% | 20 | 62 | Town |
| Hermon | 28 | 1,109 | 1,076 | 0.45% | 21 | 53 | Town |
| Hopkinton | 29 | 1,071 | 1,102 | -0.46% | 6 | 185 | Town |
| De Peyster | 30 | 1,068 | 1,017 | 0.66% | 25 | 43 | Town |
| Edwards | 31 | 975 | 1,011 | -0.81% | 19 | 50 | Town |
| Macomb | 32 | 928 | 918 | -0.64% | 15 | 61 | Town |
| Waddington | 33 | 924 | 930 | -0.11% | 424 | 2 | Village |
| Pitcairn | 34 | 794 | 792 | 0% | 14 | 59 | Town |
| Rossie | 35 | 764 | 795 | -0.78% | 20 | 38 | Town |
| Heuvelton | 36 | 703 | 714 | -0.28% | 924 | 1 | Village |
| Clifton | 37 | 674 | 678 | -0.15% | 5 | 134 | Town |
| Rensselaer Falls | 38 | 319 | 318 | 0% | 1,096 | 0 | Village |
| Hammond | 39 | 280 | 285 | -0.36% | 478 | 1 | Village |
| Piercefield | 40 | 270 | 282 | -0.74% | 3 | 104 | Town |
| Richville | 41 | 255 | 266 | -0.78% | 346 | 1 | Village |
| Clare | 42 | 91 | 96 | -1.09% | 1 | 96 | Town |
Potsdam is the largest city in St. Lawrence County, with a population of 14,090.
Clare is the smallest city in St. Lawrence County, with a population of 91.
There are 42 cities in St. Lawrence County, New York.