38 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Algonquin | 1 | 89,576 | 87,531 | 0.74% | 1,927 | 46 | Township |
| McHenry | 2 | 48,358 | 46,269 | 1.17% | 1,081 | 45 | Township |
| Crystal Lake | 3 | 41,831 | 40,240 | 0.77% | 2,203 | 19 | City |
| Nunda | 4 | 39,179 | 38,300 | 0.75% | 836 | 47 | Township |
| Algonquin | 5 | 30,754 | 29,679 | 0.7% | 2,453 | 13 | Village |
| Huntley | 6 | 28,676 | 27,769 | 0.64% | 1,957 | 15 | Village |
| Woodstock | 7 | 25,951 | 25,653 | 0.23% | 1,968 | 13 | City |
| Dorr | 8 | 21,789 | 21,550 | 0.35% | 607 | 36 | Township |
| Cary | 9 | 18,086 | 17,810 | 0.31% | 2,776 | 7 | Village |
| Greenwood | 10 | 15,463 | 14,192 | 2.05% | 438 | 35 | Township |
| Harvard | 11 | 9,395 | 9,458 | -0.14% | 1,122 | 8 | City |
| Chemung | 12 | 9,049 | 9,078 | 0.27% | 274 | 33 | Township |
| Marengo | 13 | 7,735 | 7,552 | 0.47% | 869 | 9 | City |
| Marengo | 14 | 7,385 | 7,211 | 0.87% | 205 | 36 | Township |
| Richmond | 15 | 6,839 | 6,732 | 0.47% | 208 | 33 | Township |
| Wonder Lake | 16 | 5,627 | 3,970 | 6.25% | 1,120 | 5 | Village |
| Spring Grove | 17 | 5,572 | 5,480 | 0.32% | 616 | 9 | Village |
| Burton | 18 | 4,909 | 4,876 | 0.33% | 453 | 11 | Township |
| Fox River Grove | 19 | 4,762 | 4,687 | 0.32% | 2,782 | 2 | Village |
| Coral | 20 | 3,847 | 3,621 | 2.61% | 107 | 36 | Township |
| Riley | 21 | 3,036 | 2,992 | 0.63% | 84 | 36 | Township |
| Dunham | 22 | 2,778 | 2,782 | 0.22% | 77 | 36 | Township |
| Hebron | 23 | 2,345 | 2,333 | 0.21% | 71 | 33 | Township |
| Richmond | 24 | 2,132 | 2,084 | 0.42% | 497 | 4 | Village |
| Prairie Grove | 25 | 1,950 | 1,955 | -0.05% | 321 | 6 | Village |
| Hartland | 26 | 1,893 | 1,899 | 0.16% | 53 | 36 | Township |
| Hebron | 27 | 1,399 | 1,384 | 0.21% | 715 | 2 | Village |
| Alden | 28 | 1,267 | 1,275 | 0% | 38 | 33 | Township |
| Bull Valley | 29 | 1,136 | 1,136 | 0% | 115 | 10 | Village |
| Spring Grove | 30 | 923 | 967 | -0.43% | 25 | 37 | Township |
| Union | 31 | 845 | 881 | -0.59% | 23 | 37 | Township |
| Ringwood | 32 | 836 | 840 | -0.12% | 216 | 4 | Village |
| Union | 33 | 767 | 774 | 0.13% | 21 | 36 | Township |
| Union | 34 | 725 | 550 | 5.07% | 867 | 1 | Village |
| Union | 35 | 627 | 638 | 0% | 12 | 53 | Township |
| Woodstock | 36 | 346 | 351 | 0.58% | 9 | 37 | Township |
| Greenwood | 37 | 315 | 318 | -0.32% | 119 | 3 | Village |
| Union | 38 | 201 | 205 | 0% | 6 | 35 | Township |
Algonquin is the largest city in McHenry County, with a population of 89,576.
Union is the smallest city in McHenry County, with a population of 201.
There are 38 cities in McHenry County, Illinois.