34 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Coal | 1 | 9,573 | 10,137 | -0.95% | 364 | 26 | Township |
| Sunbury | 2 | 9,511 | 9,701 | -0.4% | 4,739 | 2 | City |
| Shamokin | 3 | 6,751 | 6,929 | -0.53% | 8,183 | 1 | City |
| Milton | 4 | 6,451 | 6,610 | -0.49% | 1,860 | 3 | Borough |
| Mount Carmel | 5 | 5,599 | 5,732 | -0.48% | 8,458 | 1 | Borough |
| Delaware | 6 | 4,274 | 4,301 | 0.05% | 142 | 30 | Township |
| Ralpho | 7 | 4,180 | 4,184 | 0.1% | 226 | 18 | Township |
| Northumberland | 8 | 3,817 | 3,905 | -0.47% | 2,371 | 2 | Borough |
| Point | 9 | 3,807 | 3,834 | 0.13% | 152 | 25 | Township |
| Kulpmont | 10 | 2,683 | 2,756 | -0.56% | 2,798 | 1 | Borough |
| West Chillisquaque | 11 | 2,613 | 2,600 | -0.08% | 203 | 13 | Township |
| Mount Carmel | 12 | 2,459 | 2,483 | 0.24% | 114 | 22 | Township |
| Upper Augusta | 13 | 2,423 | 2,470 | -0.16% | 121 | 20 | Township |
| Shamokin | 14 | 2,422 | 2,372 | 0.75% | 79 | 31 | Township |
| Rockefeller | 15 | 2,304 | 2,358 | -0.26% | 112 | 21 | Township |
| Watsontown | 16 | 2,199 | 2,234 | -0.32% | 3,102 | 1 | Borough |
| Riverside | 17 | 1,995 | 2,037 | -0.45% | 404 | 5 | Borough |
| Lewis | 18 | 1,930 | 1,938 | 0.1% | 73 | 26 | Township |
| Turbot | 19 | 1,799 | 1,804 | 0.17% | 130 | 14 | Township |
| Zerbe | 20 | 1,770 | 1,802 | -0.06% | 160 | 11 | Township |
| Lower Mahanoy | 21 | 1,610 | 1,627 | 0.12% | 73 | 22 | Township |
| Rush | 22 | 1,168 | 1,195 | -0.17% | 44 | 27 | Township |
| Lower Augusta | 23 | 1,026 | 1,041 | 0% | 56 | 18 | Township |
| Jordan | 24 | 763 | 785 | -0.39% | 44 | 17 | Township |
| Turbotville | 25 | 659 | 678 | -0.6% | 1,461 | 0 | Borough |
| East Chillisquaque | 26 | 652 | 671 | -0.61% | 81 | 8 | Township |
| Upper Mahanoy | 27 | 642 | 648 | 0.16% | 28 | 23 | Township |
| East Cameron | 28 | 631 | 623 | 1.45% | 54 | 12 | Township |
| Marion Heights | 29 | 549 | 559 | -0.36% | 3,588 | 0 | Borough |
| West Cameron | 30 | 489 | 495 | 0.2% | 41 | 12 | Township |
| Little Mahanoy | 31 | 430 | 428 | 0% | 39 | 11 | Township |
| Herndon | 32 | 342 | 351 | -0.58% | 432 | 1 | Borough |
| Snydertown | 33 | 314 | 322 | -0.63% | 91 | 3 | Borough |
| McEwensville | 34 | 285 | 287 | -0.35% | 2,436 | 0 | Borough |
Coal is the largest city in Northumberland County, with a population of 9,573.
McEwensville is the smallest city in Northumberland County, with a population of 285.
There are 34 cities in Northumberland County, Pennsylvania.