The Family History Library has microfilm copies of the U.S. federal censuses for the state of Idaho for 1900, 1910, 1920, and 1930.
1870 United States Census---A free internet index and images can be viewed on FamilySearch Record Pilot site. This index includes the full name, age, sex, race, birthplace, occupation, month if born in census year, month if married in census year, birth place of father and mother, if born in a foreign country.
The 1890 federal census wasdestroyed. However, the State of Idaho is attempting to reconstruct the 1890 census by indexing a variety of records, 1885-1894, for the counties in existence for those years. This is a work in progress and is being done by staff, interns, and volunteers of the Idaho State Historical Society Public Archives and Research Library in Boise. As counties are indexed, they are added to the statewide index, which is available online.
1900 Federal Census - A free Internet index and images to the 1900 United States Census can be viewed on the FamilySearch Record Search – Pilot Site. Important additions to this census are month and year of birth of each household member, number of years married for each married person, number of children born to each mother and the number of those still living, year of immigration, and number of years in the United States.
Federal census records were taken every ten years, 1790 through 2000. Microfilm copies of the years 1790 through 1930 are available at the Family History Library, the National Archives, and other federal and state archives (for those states or territories in existence at each taking of the census). All released censuses have been indexed by at least two commercial companies and are available online for a fee. The 1880 federal census has also been indexed on FamilySearch.org. The Family History Library also has a soundex (phonetic) index on microfilm for the 1900 and 1920 censuses.
The 1940 thru 2000 census schedules are considered confidential and have not been released for public view.
Statewide indexes are available for the 1870 and 1880 censuses in book and microfiche format. A Soundex (phonetic) index is available on microfilm for part of the 1880 census. The censuses and indexes are at the Family History Library.
1870-1880--Mortality schedules exist for the 1870 and 1880 censuses. The Family History Library has the schedules and indexes.
The 1870 and 1880 non-population schedules for Idaho are also online on the Idaho Historical Society's web site, in an alphabetical listing.
Idaho does not have a state census.
The area that is presently Idaho was included in the federal censuses of the Oregon Territory (1850), Washington Territory (1860), and Idaho Territory (1870 and 1880). For the 1860 census of Idaho County, see Spokane County, Washington. Parts of southern Idaho were also included in the 1860 and 1870 censuses of Cache County, Utah.
Heritage Quest Online: http://www.heritagequestonline.com
Census Online: http://www.census-online.com/links/ID/
Genealogy Today: http://dir.genealogytoday.com/usa/id/census.html
Access Genealogy: http://www.accessgenealogy.com/census/idaho.htm
Mortality Schedules: http://mortalityschedules.com/
Idaho Research Outline. Salt Lake City, Utah: Intellectual Reserve, Inc., Family History Department, 1998, 2006.