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 |
|---|---|---|---|---|---|---|---|
| Crystal Lake | 1 | 41,071 | 40,229 | 0.51% | 2,163 | 19.0 | City |
| Algonquin | 2 | 30,286 | 29,676 | 0.5% | 2,415 | 12.5 | Village |
| Huntley | 3 | 28,436 | 27,766 | 0.59% | 1,941 | 14.7 | Village |
| Woodstock | 4 | 25,730 | 25,605 | 0.12% | 1,951 | 13.2 | City |
| Cary | 5 | 18,034 | 17,804 | 0.32% | 2,768 | 6.5 | Village |
| Harvard | 6 | 9,323 | 9,455 | -0.35% | 1,113 | 8.4 | City |
| Marengo | 7 | 7,625 | 7,555 | 0.22% | 857 | 8.9 | City |
| Spring Grove | 8 | 5,522 | 5,480 | 0.18% | 610 | 9.1 | Village |
| Wonder Lake | 9 | 5,196 | 3,966 | 6.28% | 1,047 | 5.0 | Village |
| Fox River Grove | 10 | 4,596 | 4,686 | -0.5% | 2,685 | 1.7 | Village |
| Richmond | 11 | 2,122 | 2,089 | 0.38% | 495 | 4.3 | Village |
| Prairie Grove | 12 | 1,942 | 1,960 | -0.26% | 336 | 5.8 | Village |
| Hebron | 13 | 1,388 | 1,383 | 0.07% | 709 | 2.0 | Village |
| Bull Valley | 14 | 1,111 | 1,118 | -0.18% | 115 | 9.6 | Village |
| Ringwood | 15 | 818 | 829 | -0.36% | 212 | 3.9 | Village |
| Union | 16 | 608 | 550 | 2.36% | 727 | 0.8 | Village |
| Solon Mills | 17 | 471 | 177 | 7.53% | 2,415 | 0.2 | CDP |
| Ridgefield | 18 | 443 | 274 | 7.52% | 847 | 0.5 | CDP |
| Greenwood | 19 | 314 | 317 | -0.32% | 118 | 2.7 | Village |
| Burtons Bridge | 20 | 246 | 273 | 7.42% | 2,000 | 0.1 | CDP |
| Alden | 21 | 196 | 167 | 7.69% | 1,556 | 0.1 | CDP |
| Hartland | 22 | 136 | 156 | 7.09% | 426 | 0.3 | CDP |
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.
Crystal Lake is the largest city in McHenry County.
Hartland is the smallest city in McHenry County.
There are 22 cities in McHenry County, Illinois.