10 cities
| City | County | 2026 Pop. ↓ |
|---|---|---|
| University City | St. Louis County | 33,938 |
| Union | Franklin County | 13,600 |
| Unionville | Putnam County | 1,637 |
| Urich | Henry County | 480 |
| Urbana | Dallas County | 415 |
| Union Star | DeKalb County | 375 |
| Uplands Park | St. Louis County | 301 |
| Utica | Livingston County | 222 |
| Unity Village | Jackson County | 58 |
| Umber View Heights | Cedar County | 45 |