Although the decennial census collects a variety of information that has been used in demographic studies, marketing, and other enterprises, the purpose of the census as stated in the Constitution is to produce an "actual enumeration" of the number of persons in the states in order to calculate their Congressional apportionment.
Total population counts for the Censuses of 1790 through 1860 include both free and enslaved persons.
Native Americans were not identified in the Census of 1790 through 1840 and only sporadically from 1850 until 1890, if they lived outside of Indian Territory or off reservations.
Beginning with the 1900 census, Native Americans were fully enumerated along with the general population.
Minor Outlying Islands that have never had a population enumerated by the U.S. Census Bureau are not included.
[5] Several territories and possessions held by the United States during the 1800s and 1900s gained independence or were transferred to other nations.