The first step in census research is federal census records. The federal census has been done every 10 since 1790 and the census records from 1790 to 1930 are available at the National Archives-Rocky Mountain Region located at the Federal Center in Lakewood. If you already have the federal census records for your ancestor, why go to the trouble of finding state census records?
Usually a state census was done between federal census years. While the federal census was in years ending in 0, many state census were done on the fifth year of a decade. Those that are especially important are the ones that fall between gaps in the federal census such as 1885 and 1895 (most of the1890 census was lost in a fire). A 1905 or 1915 state census can be equally important if the 1910 Federal Census was unreadable because of poor filming.
The questions asked on a state census can be different than the ones asked on the federal census. For instance, the 1925 New York State Census asks how long a person was living in the U.S. as well as the date and place of naturalization.
I can not discuss state census records without mentioning the 1925 Iowa State Census. This census has the absolute best genealogical information of any state census. In addition to the normal questions that appear on most census records such as name, age, etc., the 1925 Iowa State Census asks if the person was foreign born, year of naturalization, number of years in U.S., number of years in Iowa, level of education, names of parents (including mother’s maiden name), parents place of birth and age if living, place of parent’s marriage and military service questions. State census records can be an invaluable source when trying to solve problems or simply to gain additional information on your family. Here is an example of how state census records helped with my research.
James Crooks was born 2 July 1843 in Meigs County, Ohio and he died 21 August 1926 in Brown County, Kansas. His age in 1861 was 21. Yet I had no record that indicated he had served in the Civil War. I had collected the following records on James: Kansas State death certificate (1926), obituary, 1850, 1860, 1870, 1880, 1900, 1910, and 1920 Federal Census. Other searches which proved to be negative: the 1890 Veteran and Widow schedule for Kansas could not be checked (it was destroyed) and there was no listing in the Civil War databases on Ancestry.com. In short, there was no supporting evidence to prove James had been a soldier in the Civil War.
According to his obituary, James moved to Kansas about 1882. Therefore, James should be in the 1885, 1895, 1905, 1915, and 1925 Kansas State Census. The Kansas State Census is on microfilm and is arranged by county, then city or township. After I found Brown County on the microfilm, I went to the town of Hiawatha. I then looked for the address of 302 S. 8th Street.
The 1915 Kansas State census provided the information that James Crooks had served in Co. B, 140th Ohio Infantry. With this information, I was able to order his Civil War Military and Pension Files. These files had a wealth of information on James and his family. Without the information provided by the Kansas State Census record, I may never have proved that James was a Civil War Veteran.
There are indexes for some state census records but in general they are not as readily available as the federal census indexes. It will normally take more time and effort to access and research state census records than federal census indexes.
Generally state census records are found in the state where the census was taken, usually at the state archives or state library. Many are available on microfilm through the Family History Library and some are available through interlibrary loan.
For more information on state census records, check State Census Records by Ann Lainhart.