“IPUMS USA makes freely available to researchers worldwide complete count U.S. Census microdata through 1940. This dataset includes over 650 million individual-level (1850-1940) and 7.5 million household-level records (1790-1840). The microdata represents the fruition of longstanding collaborations between IPUMS and the nation’s two largest genealogical organizations —Ancestry.com and FamilySearch— to leverage genealogical data for scientific purposes. This microdata collection is possible due to the donations of an unprecedented scale of digitized census data by both Ancestry.com and FamilySearch. Person-level microdata are available from 1850-1940. Complete count data for 1790-1840 are available at the household-level. In contrast to the 1850-1940 U.S. censuses, the 1790-1840 historical censuses named only the head of the household and tallied household totals attached to that record.

IPUMS is continually improving the quality of these datasets by removing duplicate records, improving identification of household groups, applying numeric codes to the transcribed responses, etc. These improvements to the underlying data are periodically released via IPUMS USA. The variable VERSIONHIST identifies the public-release version of a dataset. Researchers can merge data between versions of the dataset using HISTID and identify updates, corrections, or improvements that may have been applied to the data. All data are coded and anonymous and can be downloaded via the IPUMS USA extract system. Restricted versions of these datasets are also available.”