| City | County | 2026 Pop. ↓ |
|---|---|---|
| University City | St. Louis County | 34,444 |
| Union | Franklin County | 13,651 |
| Unionville | Putnam County | 1,649 |
| Urich | Henry County | 480 |
| Urbana | Dallas County | 414 |
| Union Star | DeKalb County | 371 |
| Uplands Park | St. Louis County | 303 |
| Utica | Livingston County | 221 |
| Unity Village | Jackson County | 61 |
| Umber View Heights | Cedar County | 43 |