Admitted to the Union on May 29, 1848 as the 30th state. Wisconsin became a territory in 1836 but the area was enumerated in 1820, 1830, and 1840.
- 1820 – 1940 federal censuses extant for all counties except for 1940.
| Adams | Ashland | Barron | Bayfield |
| Brown | Buffalo | Burnett | Calumet |
| Chippewa | Clark | Columbia | Crawford |
| Dane | Dodge | Door | Douglas |
| Dunn | Eau Claire | Florence | Fond Du Lac |
| Forest | Grant | Green | Green Lake |
| Iowa | Iron | Jackson | Jefferson |
| Juneau | Kenosha | Kewaunee | La Crosse |
| Lafayette | Langlade | Lincoln | Manitowoc |
| Marathon | Marinette | Marquette | Menominee |
| Milwaukee | Monroe | Oconto | Oneida |
| Outagamie | Ozaukee | Pepin | Pierce |
| Polk | Portage | Price | Racine |
| Richland | Rock | Rusk | St. Croix |
| Sauk | Sawyer | Shawano | Sheboygan |
| Taylor | Trempealeau | Vernon | Vilas |
| Walworth | Washburn | Washington | Waukesha |
| Waupaca | Waushara | Winnebago | Wood |