Admitted to the Union on July 3, 1890 as the 43rd state. Prior to statehood, the portion above 46° north was enumerated as part of Washington Territory in 1860. Idaho became a territory in 1863.

  • 1870—1940 federal censuses extant for all counties except for 1890.
Ada Adams Bannock Bear Lake
Benewah Bingham Blaine Boise
Bonner Bonneville Boundary Butte
Camas Canyon Caribou Cassia
Clark Clearwater Custer Elmore
Franklin Fremont Gem Gooding
Idaho Jefferson Jerome Kootenai
Latah Lemhi Lewis Lincoln
Madison Minidoka Nez Perce Oneida
Owyhee Payette Power Shoshone
Teton Twin Falls Valley Washington