The United States has collected data about its population since 1790 and continues to collect data every 10 years. Currently, the National Archives has the 1790 to 1940 Federal census records available to the public.
In addition to the censuses conducted by the federal government, many state censuses have been conducted. Some of these date to the colonial period. Although the National Archives may have some of these records, contact your state or local archives to inquire about their state census holdings.
State censuses often can serve as substitutes for some of the missing federal census records - most notably the 1790, 1800, 1810, and 1890 censuses. Many state censuses also asked different questions than the federal census, thus recording information that cannot be found elsewhere in the federal schedules.
While not all states took their own censuses, and some have not survived, state and local census records can be found in many locations. Most states which took censuses usually did so every 10 years, in years ending in "5" (1855, 1865, etc.) to complement the federal census. These state census records are most often found at the state archives or state library. Many are also on microfilm through a local Family History Center of the Church of Jesus Christ of Latter-day Saints and online via commercial genealogy databases.
National level resources: