| Enumerated Area | pre1851 | 1851 | 1861 | 1871 | 1881 | 1891 | 1901 | 1911 |
| Udora Village | ONT | |||||||
| Uffington | MUS | |||||||
| Unback Twp | TBRR | |||||||
| Underwood Village | BRU | |||||||
| Unincorporated | VIC | |||||||
| Union Village | ELG | |||||||
| Union Village | ESS | |||||||
| Unionville Village | YOR | |||||||
| Uno Park Village | NIP | |||||||
| Unorganized Territory | REN | |||||||
| Unorganized Territory | ALG | TBRR | ||||||
| Unsurveyed Territory | NIP | |||||||
| Upper Wahnapitae | NIP | |||||||
| Usborne Twp | HUR | HUR | HUR | HUR | HUR | PER | PER | HUR |
| Utterson Village | MUS | |||||||
| Uxbridge Town | ONT | ONT | ONT | ONT | ||||
| Uxbridge Twp | ONT | ONT | ONT | ONT | ONT | ONT | ONT |