Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Le Ray | 1 | 25,514 | 25,499 | -0.47% | 347 | 73.6 | Town |
| Watertown | 2 | 24,027 | 24,546 | -0.54% | 2,660 | 9.0 | City |
| Brownville | 3 | 5,762 | 5,828 | -0.45% | 98 | 58.9 | Town |
| Wilna | 4 | 5,580 | 5,696 | -0.99% | 72 | 78.0 | Town |
| Watertown | 5 | 5,445 | 5,833 | -0.44% | 153 | 35.7 | Town |
| Adams | 6 | 4,879 | 4,946 | -0.63% | 116 | 42.2 | Town |
| Clayton | 7 | 4,612 | 4,731 | -0.95% | 56 | 82.5 | Town |
| Champion | 8 | 4,486 | 4,543 | -0.62% | 102 | 44.0 | Town |
| Alexandria | 9 | 3,682 | 3,730 | -0.59% | 51 | 72.6 | Town |
| Ellisburg | 10 | 3,298 | 3,339 | -0.6% | 39 | 85.2 | Town |
| Pamelia | 11 | 3,248 | 3,325 | -0.73% | 95 | 34.1 | Town |
| Carthage | 12 | 3,247 | 3,315 | -0.52% | 1,339 | 2.4 | Village |
| Hounsfield | 13 | 3,225 | 3,260 | -0.56% | 66 | 49.0 | Town |
| Rutland | 14 | 2,965 | 3,020 | -0.77% | 66 | 45.2 | Town |
| Orleans | 15 | 2,748 | 2,782 | -0.58% | 39 | 71.3 | Town |
| Cape Vincent | 16 | 2,628 | 2,678 | 4.04% | 47 | 56.3 | Town |
| Theresa | 17 | 2,613 | 2,640 | -0.68% | 40 | 65.1 | Town |
| Lyme | 18 | 2,225 | 2,285 | -0.98% | 40 | 55.9 | Town |
| Philadelphia | 19 | 1,934 | 1,965 | -0.57% | 51 | 37.7 | Town |
| West Carthage | 20 | 1,749 | 1,767 | -0.29% | 1,337 | 1.3 | Village |
| Clayton | 21 | 1,690 | 1,733 | -0.65% | 1,055 | 1.6 | Village |
| Adams | 22 | 1,674 | 1,688 | -0.24% | 1,158 | 1.4 | Village |
| Antwerp | 23 | 1,658 | 1,679 | -0.66% | 16 | 106.0 | Town |
| Henderson | 24 | 1,420 | 1,435 | -0.49% | 34 | 41.2 | Town |
| Sackets Harbor | 25 | 1,361 | 1,372 | -0.22% | 590 | 2.3 | Village |
| Black River | 26 | 1,229 | 1,260 | -0.65% | 690 | 1.8 | Village |
| Rodman | 27 | 1,175 | 1,193 | -0.76% | 28 | 42.3 | Town |
| Philadelphia | 28 | 1,142 | 1,172 | -0.7% | 1,192 | 1.0 | Village |
| Dexter | 29 | 1,007 | 1,011 | -0.1% | 1,512 | 0.7 | Village |
| Alexandria Bay | 30 | 948 | 959 | -0.32% | 1,266 | 0.7 | Village |
| Brownville | 31 | 937 | 945 | -0.21% | 1,502 | 0.6 | Village |
| Theresa | 32 | 742 | 760 | -0.67% | 587 | 1.3 | Village |
| Cape Vincent | 33 | 726 | 734 | -0.27% | 1,033 | 0.7 | Village |
| Evans Mills | 34 | 619 | 625 | -0.32% | 758 | 0.8 | Village |
| Chaumont | 35 | 594 | 608 | -0.67% | 604 | 1.0 | Village |
| Antwerp | 36 | 510 | 516 | -0.39% | 508 | 1.0 | Village |
| Glen Park | 37 | 444 | 446 | -0.22% | 622 | 0.7 | Village |
| Mannsville | 38 | 319 | 322 | -0.31% | 356 | 0.9 | Village |
| Deferiet | 39 | 254 | 258 | -0.39% | 376 | 0.7 | Village |
| Ellisburg | 40 | 213 | 215 | -0.47% | 213 | 1.0 | Village |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Le Ray is the largest city in Jefferson County.
Ellisburg is the smallest city in Jefferson County.
There are 40 cities in Jefferson County, New York.