The United States Census of 1880, conducted during June 1880, determined the resident population of the United States to be 50,189,209 - an increase of 30.2 percent over the 1870 Census.
The 1880 census contains records of families living in the United States and its territories during the latter half of the Great Westward Migration. Thirty-eight states were included in the 1880 census, plus the territories of: Arizona, Dakota, Idaho, Montana, New Mexico, Utah, Washington, and Wyoming. Non-organized Alaska was also enumerated, but the "Indian Territory" (now Oklahoma) was not enumerated for non-Indians.
Federal census takers were asked to record information about every person who was in each household on the census day. A census taker might have visited a house on a later date, but the information he collected was supposed to be about the people who were in the house on the census day. The basic census enumeration unit was the county. Each county was divided into enumeration districts, one for each enumerator. The completed forms were sent to the Commerce Department’s Census Office in Washington, D.C.
Federal censuses are usually reliable, depending on the knowledge of the informant and the care of the census enumerator. Information may have been given to a census taker by any member of the family or by a neighbor. Some information may have been incorrect or deliberately falsified.