Additional Information may be found on the United States Census Portal page.
1890--Census was destroyed.The 1890 Union veterans schedule and index are available at the Family History Library and at the National Archives.
1900-1930--The Family History Library has the U.S. federal censuses for Montana for 1900, 1910, 1920 and 1930.
Many federal census records are found at the Family History Library, the National Archives and its regional centers, and state archives. The United States Research Outline provides more detailed information about these records.
1860s--Montana west of the continental divide was designated Missoula County, Washington Territoy in 1860. In 1861 the unsettled eastern portion was attached to Dakota Territory, In 1863 and 1864 all of Montana was included in Idaho Territory.
1864--Montana Territory was established with nine counties.
1889--Montana became a state.
1910-1925--The number of counties doubled from 28 to the present 56 as homesteaders moved into eastern Montana.
Indexes for the Montana returns for 1860, 1870, and 1880 are available in book format. Mortality schedules for the 1870 and 1880 censuses are at the Montana Historical Society and at the DAR library in Washington, DC. The Family History Library also has published indexes for the 1870 and 1880 mortality schedules.
To identify early settlers, see List of Early Settlers: A List of All Persons (Except Indians) Who Were in What Is Now Montana During the Winter of 1862-1863, compiled by the Montana Historical Society. It is found in Contributions to the Historical Society of Montana . . . , 1: 293-308, Second Edition. (Helena: Rocky Mountain Publishing Company, 1902; FHL film 1000177 item 2).
The Montana Historical Society also has a manuscript of an 1864 Montana poll list. Although not as complete as a census, it gives the names of eligible voters.
In 1860 the area that is now western Montana was part of the Washington Territory. Eastern Montana was part of the unorganized area of Nebraska Territory in 1860. The 1860 censuses for these two territories list the individuals who lived in what is now Montana. Federal censuses for Montana Territory are available for 1870 and 1880.
Heritage Quest Online: http://www.heritagequestonline.com
Census Online: http://www.census-online.com/links/MT/
Genealogy Today: http://dir.genealogytoday.com/usa/mt/census.html
Access Genealogy: http://www.accessgenealogy.com/census/montana.htm
Montana Research Outline. Salt Lake City, Utah: Intellectual Reserve, Inc., Family History Department, 1998, 2001.