38 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Algonquin | 1 | 90,237 | 87,531 | 0.74% | 1,941 | 46 | Township |
| McHenry | 2 | 48,918 | 46,269 | 1.16% | 1,094 | 45 | Township |
| Crystal Lake | 3 | 42,149 | 40,240 | 0.76% | 2,220 | 19 | City |
| Nunda | 4 | 39,470 | 38,300 | 0.74% | 842 | 47 | Township |
| Algonquin | 5 | 30,969 | 29,679 | 0.7% | 2,470 | 13 | Village |
| Huntley | 6 | 28,858 | 27,769 | 0.63% | 1,970 | 15 | Village |
| Woodstock | 7 | 26,011 | 25,653 | 0.23% | 1,972 | 13 | City |
| Dorr | 8 | 21,866 | 21,550 | 0.35% | 609 | 36 | Township |
| Cary | 9 | 18,141 | 17,810 | 0.3% | 2,784 | 7 | Village |
| Greenwood | 10 | 15,773 | 14,192 | 2% | 446 | 35 | Township |
| Harvard | 11 | 9,383 | 9,458 | -0.13% | 1,120 | 8 | City |
| Chemung | 12 | 9,073 | 9,078 | 0.27% | 275 | 33 | Township |
| Marengo | 13 | 7,772 | 7,552 | 0.48% | 873 | 9 | City |
| Marengo | 14 | 7,449 | 7,211 | 0.87% | 207 | 36 | Township |
| Richmond | 15 | 6,871 | 6,732 | 0.47% | 209 | 33 | Township |
| Wonder Lake | 16 | 5,959 | 3,970 | 5.9% | 1,187 | 5 | Village |
| Spring Grove | 17 | 5,591 | 5,480 | 0.34% | 618 | 9 | Village |
| Burton | 18 | 4,925 | 4,876 | 0.33% | 455 | 11 | Township |
| Fox River Grove | 19 | 4,777 | 4,687 | 0.31% | 2,790 | 2 | Village |
| Coral | 20 | 3,945 | 3,621 | 2.55% | 110 | 36 | Township |
| Riley | 21 | 3,055 | 2,992 | 0.63% | 85 | 36 | Township |
| Dunham | 22 | 2,784 | 2,782 | 0.22% | 77 | 36 | Township |
| Hebron | 23 | 2,350 | 2,333 | 0.21% | 71 | 33 | Township |
| Richmond | 24 | 2,142 | 2,084 | 0.47% | 500 | 4 | Village |
| Prairie Grove | 25 | 1,949 | 1,955 | -0.05% | 321 | 6 | Village |
| Hartland | 26 | 1,896 | 1,899 | 0.16% | 53 | 36 | Township |
| Hebron | 27 | 1,402 | 1,384 | 0.21% | 716 | 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 | 919 | 967 | -0.43% | 25 | 37 | Township |
| Union | 31 | 840 | 881 | -0.59% | 23 | 37 | Township |
| Ringwood | 32 | 835 | 840 | -0.12% | 216 | 4 | Village |
| Union | 33 | 768 | 774 | 0.13% | 21 | 36 | Township |
| Union | 34 | 760 | 550 | 4.83% | 909 | 1 | Village |
| Union | 35 | 627 | 638 | 0% | 12 | 53 | Township |
| Woodstock | 36 | 348 | 351 | 0.58% | 9 | 37 | Township |
| Greenwood | 37 | 315 | 318 | 0% | 119 | 3 | Village |
| Union | 38 | 201 | 205 | 0% | 6 | 35 | Township |
Algonquin is the largest city in McHenry County, with a population of 90,237.
Union is the smallest city in McHenry County, with a population of 201.
There are 38 cities in McHenry County, Illinois.