78 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Elizabeth | 1 | 142,781 | 137,310 | 1.69% | 11,590 | 12 | City |
| Elizabeth | 2 | 142,781 | 136,681 | 1.69% | 11,590 | 12 | City |
| Elizabeth | 3 | 141,346 | 137,310 | 0.66% | 11,474 | 12 | City |
| Elizabeth | 4 | 141,346 | 136,681 | 0.66% | 11,474 | 12 | City |
| Union | 5 | 64,689 | 59,740 | 2.4% | 7,147 | 9 | Township |
| Union | 6 | 64,689 | 59,829 | 2.4% | 7,147 | 9 | Township |
| Plainfield | 7 | 57,453 | 54,600 | 1.67% | 9,641 | 6 | City |
| Plainfield | 8 | 57,453 | 54,344 | 1.67% | 9,641 | 6 | City |
| Plainfield | 9 | 57,047 | 54,600 | 0.96% | 9,573 | 6 | City |
| Plainfield | 10 | 57,047 | 54,344 | 0.96% | 9,573 | 6 | City |
| Linden | 11 | 46,116 | 43,746 | 1.59% | 4,315 | 11 | City |
| Linden | 12 | 46,116 | 43,540 | 1.59% | 4,315 | 11 | City |
| Linden | 13 | 45,856 | 43,746 | 1.02% | 4,290 | 11 | City |
| Linden | 14 | 45,856 | 43,540 | 1.02% | 4,290 | 11 | City |
| Westfield | 15 | 33,036 | 31,039 | 3.08% | 4,913 | 7 | Town |
| Westfield | 16 | 33,036 | 30,898 | 3.08% | 4,913 | 7 | Town |
| Westfield | 17 | 32,338 | 31,039 | 0.9% | 4,809 | 7 | Town |
| Westfield | 18 | 32,338 | 30,898 | 0.9% | 4,809 | 7 | Town |
| Rahway | 19 | 31,224 | 29,550 | 1.5% | 8,014 | 4 | City |
| Rahway | 20 | 31,224 | 29,671 | 1.5% | 8,014 | 4 | City |
| Rahway | 21 | 31,036 | 29,550 | 0.89% | 7,966 | 4 | City |
| Rahway | 22 | 31,036 | 29,671 | 0.89% | 7,966 | 4 | City |
| Scotch Plains | 23 | 25,614 | 24,962 | 1.55% | 2,839 | 9 | Township |
| Scotch Plains | 24 | 25,614 | 24,855 | 1.55% | 2,839 | 9 | Township |
| Cranford | 25 | 24,899 | 23,831 | 1.57% | 5,150 | 5 | Township |
| Cranford | 26 | 24,899 | 23,815 | 1.57% | 5,150 | 5 | Township |
| Summit | 27 | 23,493 | 22,730 | 1.69% | 3,919 | 6 | City |
| Summit | 28 | 23,493 | 22,639 | 1.69% | 3,919 | 6 | City |
| Roselle | 29 | 23,420 | 22,694 | 1.54% | 8,888 | 3 | Borough |
| Roselle | 30 | 23,420 | 22,606 | 1.54% | 8,888 | 3 | Borough |
| Summit | 31 | 23,217 | 22,730 | 0.5% | 3,873 | 6 | City |
| Summit | 32 | 23,217 | 22,639 | 0.5% | 3,873 | 6 | City |
| Roselle | 33 | 23,178 | 22,694 | 0.49% | 8,796 | 3 | Borough |
| Roselle | 34 | 23,178 | 22,606 | 0.49% | 8,796 | 3 | Borough |
| Hillside | 35 | 23,030 | 22,448 | 1.5% | 8,323 | 3 | Township |
| Hillside | 36 | 23,030 | 22,342 | 1.5% | 8,323 | 3 | Township |
| Springfield | 37 | 18,138 | 17,185 | 2.88% | 3,517 | 5 | Township |
| Springfield | 38 | 18,138 | 17,106 | 2.88% | 3,517 | 5 | Township |
| Clark | 39 | 16,879 | 15,532 | 3.7% | 3,950 | 4 | Township |
| Clark | 40 | 16,879 | 15,464 | 3.7% | 3,950 | 4 | Township |
| Berkeley Heights | 41 | 15,532 | 13,259 | 7.04% | 2,497 | 6 | Township |
| Berkeley Heights | 42 | 15,532 | 13,203 | 7.04% | 2,497 | 6 | Township |
| Roselle Park | 43 | 14,617 | 13,962 | 1.58% | 11,932 | 1 | Borough |
| Roselle Park | 44 | 14,617 | 14,005 | 1.58% | 11,932 | 1 | Borough |
| Roselle Park | 45 | 14,486 | 13,962 | 0.67% | 11,825 | 1 | Borough |
| Roselle Park | 46 | 14,486 | 14,005 | 0.67% | 11,825 | 1 | Borough |
| New Providence | 47 | 14,182 | 13,663 | 1.61% | 3,845 | 4 | Borough |
| New Providence | 48 | 14,182 | 13,704 | 1.61% | 3,845 | 4 | Borough |
| New Providence | 49 | 14,020 | 13,663 | 0.45% | 3,802 | 4 | Borough |
| New Providence | 50 | 14,020 | 13,704 | 0.45% | 3,802 | 4 | Borough |
| Kenilworth | 51 | 8,660 | 8,429 | 1.56% | 4,034 | 2 | Borough |
| Kenilworth | 52 | 8,660 | 8,392 | 1.56% | 4,034 | 2 | Borough |
| Kenilworth | 53 | 8,560 | 8,429 | 0.39% | 3,987 | 2 | Borough |
| Kenilworth | 54 | 8,560 | 8,392 | 0.39% | 3,987 | 2 | Borough |
| Fanwood | 55 | 8,154 | 7,783 | 2.33% | 6,085 | 1 | Borough |
| Fanwood | 56 | 8,154 | 7,749 | 2.33% | 6,085 | 1 | Borough |
| Fanwood | 57 | 8,022 | 7,783 | 0.68% | 5,987 | 1 | Borough |
| Fanwood | 58 | 8,022 | 7,749 | 0.68% | 5,987 | 1 | Borough |
| Mountainside | 59 | 7,417 | 7,024 | 2.61% | 1,856 | 4 | Borough |
| Mountainside | 60 | 7,417 | 6,992 | 2.61% | 1,856 | 4 | Borough |
| Mountainside | 61 | 7,287 | 7,024 | 0.82% | 1,824 | 4 | Borough |
| Mountainside | 62 | 7,287 | 6,992 | 0.82% | 1,824 | 4 | Borough |
| Union | 63 | 6,671 | 6,507 | 2.07% | 356 | 19 | Township |
| Union | 64 | 6,671 | 6,495 | 2.07% | 356 | 19 | Township |
| Vauxhall | 65 | 6,664 | 5,677 | 7.14% | 11,314 | 1 | CDP |
| Garwood | 66 | 5,575 | 4,451 | 4.28% | 8,577 | 1 | Borough |
| Garwood | 67 | 5,575 | 4,430 | 4.28% | 8,577 | 1 | Borough |
| Garwood | 68 | 5,445 | 4,451 | 1.85% | 8,377 | 1 | Borough |
| Garwood | 69 | 5,445 | 4,430 | 1.85% | 8,377 | 1 | Borough |
| Union | 70 | 3,718 | 2,591 | 7.15% | 14,580 | 0 | CDP |
| Springfield | 71 | 3,324 | 3,242 | 0.94% | 113 | 30 | Township |
| Springfield | 72 | 3,324 | 3,239 | 0.94% | 113 | 30 | Township |
| Cranford | 73 | 2,160 | 2,008 | 7.14% | 6,409 | 0 | CDP |
| Springfield | 74 | 1,826 | 1,498 | 7.16% | 4,706 | 0 | CDP |
| Kean University | 75 | 1,640 | 1,187 | 7.12% | 5,616 | 0 | CDP |
| Winfield | 76 | 1,461 | 1,422 | 1.6% | 8,072 | 0 | Township |
| Winfield | 77 | 1,461 | 1,415 | 1.6% | 8,072 | 0 | Township |
| Connecticut Farms | 78 | 629 | 566 | 7.16% | 6,837 | 0 | CDP |
Elizabeth is the largest city in Union County, with a population of 142,781.
Connecticut Farms is the smallest city in Union County, with a population of 629.
There are 78 cities in Union County, New Jersey.