17 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Crystal Lake | 1 | 42,149 | 40,240 | 0.76% | 2,220 | 19 | City |
| Algonquin | 2 | 30,969 | 29,679 | 0.7% | 2,470 | 13 | Village |
| Huntley | 3 | 28,858 | 27,769 | 0.63% | 1,970 | 15 | Village |
| Woodstock | 4 | 26,011 | 25,653 | 0.23% | 1,972 | 13 | City |
| Cary | 5 | 18,141 | 17,810 | 0.3% | 2,784 | 7 | Village |
| Harvard | 6 | 9,383 | 9,458 | -0.13% | 1,120 | 8 | City |
| Marengo | 7 | 7,772 | 7,552 | 0.48% | 873 | 9 | City |
| Wonder Lake | 8 | 5,959 | 3,970 | 5.9% | 1,187 | 5 | Village |
| Spring Grove | 9 | 5,591 | 5,480 | 0.34% | 618 | 9 | Village |
| Fox River Grove | 10 | 4,777 | 4,687 | 0.31% | 2,790 | 2 | Village |
| Richmond | 11 | 2,142 | 2,084 | 0.47% | 500 | 4 | Village |
| Prairie Grove | 12 | 1,949 | 1,955 | -0.05% | 321 | 6 | Village |
| Hebron | 13 | 1,402 | 1,384 | 0.21% | 716 | 2 | Village |
| Bull Valley | 14 | 1,136 | 1,136 | 0% | 115 | 10 | Village |
| Ringwood | 15 | 835 | 840 | -0.12% | 216 | 4 | Village |
| Union | 16 | 760 | 550 | 4.83% | 909 | 1 | Village |
| Greenwood | 17 | 315 | 318 | 0% | 119 | 3 | Village |
Crystal Lake is the largest city in McHenry County, with a population of 42,149.
Greenwood is the smallest city in McHenry County, with a population of 315.
There are 17 cities in McHenry County, Illinois.