43 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Algonquin township | 1 | 88,836 | 87,515 | 0.42% | 1,911 | 46.49 | Township |
| McHenry township | 2 | 47,462 | 46,231 | 0.36% | 1,061 | 44.72 | Township |
| Crystal Lake | 3 | 41,282 | 40,229 | 0.51% | 2,174 | 18.98 | City |
| Nunda township | 4 | 38,633 | 38,305 | 0.14% | 824 | 46.86 | Township |
| Algonquin | 5 | 30,439 | 29,676 | 0.51% | 2,428 | 12.54 | Village |
| Huntley | 6 | 28,604 | 27,766 | 0.59% | 1,952 | 14.65 | Village |
| Woodstock | 7 | 25,761 | 25,605 | 0.12% | 1,954 | 13.19 | City |
| Dorr township | 8 | 21,652 | 21,542 | 0.15% | 603 | 35.92 | Township |
| Cary | 9 | 18,092 | 17,804 | 0.32% | 2,777 | 6.52 | Village |
| Greenwood township | 10 | 15,415 | 14,168 | 2.04% | 436 | 35.33 | Township |
| Harvard | 11 | 9,290 | 9,455 | -0.35% | 1,109 | 8.38 | City |
| Chemung township | 12 | 8,937 | 9,078 | -0.26% | 271 | 33.01 | Township |
| Marengo | 13 | 7,643 | 7,555 | 0.24% | 859 | 8.90 | City |
| Marengo township | 14 | 7,321 | 7,215 | 0.51% | 204 | 35.95 | Township |
| Richmond township | 15 | 6,813 | 6,731 | 0.37% | 207 | 32.87 | Township |
| Spring Grove | 16 | 5,533 | 5,480 | 0.2% | 611 | 9.05 | Village |
| Wonder Lake | 17 | 5,504 | 3,966 | 5.93% | 1,109 | 4.96 | Village |
| Burton township | 18 | 4,890 | 4,879 | 0.18% | 452 | 10.83 | Township |
| Fox River Grove | 19 | 4,574 | 4,686 | -0.48% | 2,672 | 1.71 | Village |
| Coral township | 20 | 3,738 | 3,619 | 1.3% | 104 | 35.98 | Township |
| Riley township | 21 | 3,003 | 2,991 | 0.2% | 83 | 35.98 | Township |
| Dunham township | 22 | 2,755 | 2,781 | -0.07% | 77 | 35.94 | Township |
| Hebron township | 23 | 2,318 | 2,331 | -0.22% | 70 | 33.04 | Township |
| Richmond | 24 | 2,130 | 2,089 | 0.38% | 497 | 4.29 | Village |
| Prairie Grove | 25 | 1,938 | 1,960 | -0.21% | 335 | 5.78 | Village |
| Hartland township | 26 | 1,870 | 1,890 | -0.16% | 52 | 35.74 | Township |
| Hebron | 27 | 1,389 | 1,383 | 0.07% | 710 | 1.96 | Village |
| Alden township | 28 | 1,262 | 1,275 | -0.08% | 38 | 33.20 | Township |
| Bull Valley | 29 | 1,109 | 1,118 | -0.18% | 115 | 9.65 | Village |
| Spring Grove township | 30 | 917 | 972 | -0.97% | 25 | 36.84 | Township |
| Union township | 31 | 829 | 881 | -1.43% | 23 | 36.60 | Township |
| Ringwood | 32 | 815 | 829 | -0.37% | 211 | 3.86 | Village |
| Union township | 33 | 760 | 773 | -0.13% | 21 | 35.79 | Township |
| Union | 34 | 623 | 550 | 2.47% | 745 | 0.84 | Village |
| Union township | 35 | 614 | 638 | -0.81% | 12 | 52.73 | Township |
| Solon Mills | 36 | 505 | 177 | 7.22% | 2,590 | 0.20 | CDP |
| Ridgefield | 37 | 475 | 274 | 7.22% | 908 | 0.52 | CDP |
| Woodstock township | 38 | 346 | 352 | 0% | 9 | 37.31 | Township |
| Greenwood | 39 | 313 | 317 | -0.32% | 118 | 2.66 | Village |
| Burtons Bridge | 40 | 264 | 273 | 7.32% | 2,146 | 0.12 | CDP |
| Alden | 41 | 210 | 167 | 7.14% | 1,667 | 0.13 | CDP |
| Union township | 42 | 196 | 204 | -1.01% | 6 | 35.23 | Township |
| Hartland | 43 | 146 | 156 | 7.35% | 458 | 0.32 | CDP |
Algonquin township is the largest city in McHenry County, with a population of 88,836.
Hartland is the smallest city in McHenry County.
There are 43 cities in McHenry County, Illinois.