Admitted to the Union on November 8, 1889 as the 41st state. Montana east of the Continental Divide was part of Nebraska Territory in 1860, but for convenience the trading posts called Fort Alexander and Fort Union were enumerated with unorganized Dakota. Montana west of the divide was enumerated as the Bitter Root Valley in Spokane County, Washington Territory. Montana became a territory in 1864.

  • 1860 federal census extant for Spokane County, Washington Territory, and Forts Alexander and Union, unorganized Dakota are extant.
  • 1870 – 1940 federal censuses extant for all counties except for 1890.
Beaverhead Big Horn Blaine Broadwater
Carbon Carter Cascade Chouteau
Custer Daniels Dawson Deer Lodge
Fallon Fergus Flathead Gallatin
Garfield Glacier Golden Valley Granite
Hill Jefferson Judith Basin Lake
Lewis And Clark Liberty Lincoln Madison
McCone Meagher Mineral Missoula
Musselshell Park Petroleum Phillips
Pondera Powder River Powell Prairie
Ravalli Richland Roosevelt Rosebud
Sanders Sheridan Silver Bow Stillwater
Sweet Grass Teton Toole Treasure
Valley Wheatland Wibaux Yellowstone
Yellowstone National Park