1790–1899: see Table Aa9–14. 1900–1989: U.S. Bureau of the Census, Current Population Reports, series P-25, numbers 499, 1045, and 1126. 1990–2000: U.S. Bureau of the Census, Statistical Abstract of the United States, 2002, Table 2.

Estimates for 1790–1899 are based on the methodology described in the text for Table Aa9–14. Estimates for the 1900–1919 period are based on interpolation techniques applied to census age data. Estimates for subsequent years are based on census data and information on births, deaths, and international migration. Annual national population estimates start with decennial census data as benchmarks and add annual population component of change data. Component of change data are obtained from various agencies: births and deaths (National Center for Health Statistics), legal immigrants (Immigration and Naturalization Service), refugees (Office of Refugee Resettlement), net movement between Puerto Rico and the U.S. mainland (U.S. Census Bureau's International Programs Center), and movement of military and civilian citizens abroad (Department of Defense and Office of Personnel Management). Emigration and net undocumented immigration are projected based on research using census data.

The estimates are as of July 1, and thus figures for the resident population for census years differ from decennial census populations.

Alaska and Hawai'i are included beginning in 1950.

Estimates subsequent to the 1990 Census reflect the final results of the 2000 Census.

Population estimates are published in the P-25 series of Current Population Reports and as Population Paper Listings (PPLs). These estimates are generally consistent with official decennial census figures and do not reflect the amount of estimated census underenumeration. The estimates by race, however, have been modified and are not necessarily comparable to the census race categories.

For a discussion of the methodology, see the following: for 1940–1949 and 1950–1959, Bureau of the Census, Current Population Reports, series P-25, number 311, pp. 1–3; for 1960–1969, number 519, pp. 1–11; for 1970–1979, number 917, pp. 1–7; for 1980–1989, number 1095, pp. v–xxi, and Frederick W. Hollmann, Lisa B. Kuzmekus, et al., “U.S. Population by Age, Sex, Race, and Hispanic Origin: 1990 to 1997,” U.S. Bureau of the Census PPL-91 and appendixes.