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 |
|---|---|---|---|---|---|---|---|
| Coal township | 1 | 10,020 | 10,123 | 2.91% | 381 | 26.3 | Township |
| Sunbury | 2 | 9,484 | 9,704 | -0.58% | 4,725 | 2.0 | City |
| Shamokin | 3 | 6,760 | 6,930 | -0.63% | 8,194 | 0.8 | City |
| Milton | 4 | 6,457 | 6,615 | -0.62% | 1,861 | 3.5 | Borough |
| Mount Carmel | 5 | 5,604 | 5,727 | -0.55% | 8,465 | 0.7 | Borough |
| Delaware township | 6 | 4,270 | 4,298 | -0.02% | 142 | 30.1 | Township |
| Ralpho township | 7 | 4,180 | 4,186 | 0.12% | 226 | 18.5 | Township |
| Northumberland | 8 | 3,816 | 3,906 | -0.6% | 2,370 | 1.6 | Borough |
| Point township | 9 | 3,778 | 3,831 | -0.37% | 151 | 25.1 | Township |
| Kulpmont | 10 | 2,685 | 2,757 | -0.67% | 2,800 | 1.0 | Borough |
| West Chillisquaque township | 11 | 2,640 | 2,602 | 0.65% | 205 | 12.9 | Township |
| Mount Carmel township | 12 | 2,441 | 2,489 | -0.37% | 113 | 21.6 | Township |
| Upper Augusta township | 13 | 2,419 | 2,472 | -0.53% | 121 | 20.0 | Township |
| Shamokin township | 14 | 2,388 | 2,372 | 0.21% | 77 | 30.8 | Township |
| Rockefeller township | 15 | 2,305 | 2,359 | -0.6% | 112 | 20.6 | Township |
| Watsontown | 16 | 2,206 | 2,236 | -0.36% | 3,111 | 0.7 | Borough |
| Riverside | 17 | 2,004 | 2,040 | -0.45% | 406 | 4.9 | Borough |
| Lewis township | 18 | 1,919 | 1,938 | -0.36% | 73 | 26.4 | Township |
| Turbot township | 19 | 1,792 | 1,799 | 0.17% | 130 | 13.8 | Township |
| Zerbe township | 20 | 1,762 | 1,802 | -0.51% | 159 | 11.1 | Township |
| Lower Mahanoy township | 21 | 1,600 | 1,627 | -0.37% | 73 | 22.0 | Township |
| Rush township | 22 | 1,164 | 1,194 | -0.68% | 44 | 26.6 | Township |
| Lower Augusta township | 23 | 1,020 | 1,042 | -0.58% | 56 | 18.3 | Township |
| Turbotville | 24 | 659 | 677 | -0.75% | 1,461 | 0.5 | Borough |
| Marion Heights | 25 | 548 | 558 | -0.54% | 3,582 | 0.2 | Borough |
| Herndon | 26 | 342 | 350 | -0.58% | 432 | 0.8 | Borough |
| Snydertown | 27 | 320 | 328 | -0.62% | 93 | 3.4 | Borough |
| McEwensville | 28 | 288 | 290 | -0.35% | 2,462 | 0.1 | Borough |
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.
Coal township is the largest city in Northumberland County.
McEwensville is the smallest city in Northumberland County.
There are 28 cities in Northumberland County, Pennsylvania.