19 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Helena | 1 | 35,347 | 32,112 | 1.78% | 2,093 | 17 | City |
| Helena | 2 | 35,347 | 32,255 | 1.78% | 2,093 | 17 | City |
| Helena Valley Southeast | 3 | 9,661 | 8,546 | 1% | 450 | 21 | CDP |
| Helena Valley West Central | 4 | 8,287 | 8,042 | 0.33% | 314 | 26 | CDP |
| Helena Valley Northwest | 5 | 5,558 | 4,256 | 2.55% | 339 | 16 | CDP |
| Helena Valley Northeast | 6 | 4,558 | 3,519 | 2.36% | 86 | 53 | CDP |
| East Helena | 7 | 2,311 | 1,945 | 3.22% | 570 | 4 | City |
| East Helena | 8 | 2,311 | 1,948 | 3.22% | 570 | 4 | City |
| Helena West Side | 9 | 1,580 | 1,656 | -0.19% | 103 | 15 | CDP |
| Lincoln | 10 | 1,003 | 1,017 | -0.1% | 57 | 18 | CDP |
| Unionville | 11 | 436 | 151 | 7.13% | 340 | 1 | CDP |
| York | 12 | 292 | 158 | 6.96% | 890 | 0 | CDP |
| Augusta | 13 | 191 | 238 | -4.02% | 207 | 1 | CDP |
| Rimini | 14 | 111 | 110 | 6.73% | 365 | 0 | CDP |
| Marysville | 15 | 75 | 71 | 7.14% | 151 | 0 | CDP |
| Canyon Creek | 16 | 74 | 71 | 7.25% | 101 | 1 | CDP |
| Craig | 17 | 49 | 16 | 6.52% | 164 | 0 | CDP |
| Gilman | 18 | 31 | 41 | 6.9% | 47 | 1 | CDP |
| Wolf Creek | 19 | 15 | 22 | 7.14% | 70 | 0 | CDP |
Helena is the largest city in Lewis and Clark County, with a population of 35,347.
Wolf Creek is the smallest city in Lewis and Clark County, with a population of 15.
There are 19 cities in Lewis and Clark County, Montana.