Idaho is divided into political jurisdictions designated as counties.
Since 1919 there are 44 counties in the state, ranging in size from 410 to 8,502 square miles.

County County seat Year
founded
Administrator
Ada Boise 1864  
Adams Council 1911  
Bannock Pocatello 1893  
Bear Lake Paris 1893  
Benewah St. Maries 1915  
Bingham Blackfoot 1885  
Blaine Hailey 1895  
Boise Idaho City 1864  
Bonner Sandpoint 1907  
Bonneville Idaho Falls 1911  
Boundary Bonners Ferry 1915  
Butte Arco 1917  
Camas Fairfield 1917  
Canyon Caldwell 1891  
Caribou Soda Springs 1919  
Cassia Burley 1879  
Clark Dubois 1919  
Clearwater Orofino 1911  
Custer Challis 1881  
Elmore Mountain Home 1889  
Franklin Preston 1913  
Fremont St. Anthony 1893  
Gem Emmett 1915  
Gooding Gooding 1913  
Idaho Grangeville 1861/1864  
Jefferson Rigby 1913  
Jerome Jerome 1919  
Kootenai Coeur d'Alene 1864  
Latah Moscow 1888  
Lemhi Salmon 1869  
Lewis Nezperce 1911  
Lincoln Shoshone 1895  
Madison Rexburg 1914  
Minidoka Rupert 1913  
Nez Perce Lewiston 1861/1864  
Oneida Malad City 1864  
Owyhee Murphy 1863  
Payette Payette 1917  
Power American Falls 1913  
Shoshone Wallace 1861/1864  
Teton Driggs 1915  
Twin Falls Twin Falls 1907  
Valley Cascade 1917  
Washington Weiser 1879