The United States Census of 1870 was the ninth United States Census. Conducted by the Census Bureau in June 1870, the 1870 Census was the first census to provide detailed information on the black population, only years after the culmination of the Civil War when slaves were granted freedom. The population was said to be 38,555,983 individuals, a 22.62% increase since 1860. The 1870 Census' population estimate is controversial, as many believed it underestimated the true population numbers, especially in New York and Pennsylvania.
Under the Census Act of 1850, two new structural changes during the 1870 Census occurred: marshals had to return the completed population questionnaire to the Census Office in September and penalties for refusing to reply to enumerator questions were extended to encompass every question on the questionnaires.
The commonly past-used slave questionnaires were redesigned to reflect the American society after the Civil War. The five schedules for the 1870 Census were the following: General Population, Mortality, Agriculture, Products of Industry, and Social Statistics.
Mortality rates in 1870, in general, decreased as a fraction of the total population by 0.03% from 1860 and by 0.11% from 1850. The lower death rates indicate that the standard of living increased, due to some exogenous factor, over the period of twenty years from 1850 to 1870.
In terms of products of industry, total U.S. wealth increases by 17.3% from 1860 to 1870, to reach an assessed wealth of $14,178,986,732. The four main state contributors to this wealth were New York, Massachusetts, Pennsylvania, and Ohio, in that order. Most of the wealth was concentrated in the developed Northeast region, as newer states like Wyoming were beginning to develop their young economies.
The 1870 Census was the first of its kind to record the nativity of the American population. This social statistic indicates which areas were more highly composed of immigrants than native-born Americans. New York City had the most foreign-born individuals, with 419,094 foreigners, who comprised 44.5% of the city's total population. Philadelphia, Chicago, St. Louis, and San Francisco also had a great population of foreigners that made up a significant fraction of their total populations. Therefore, a great ethnic and cultural change was witnessed from 1860 to 1870, as part of the population growth was due to immigrants moving in and a shuffling of residents across state borders.
Although Francis Walker, the Superintendent of the 1870 Census, defended the quality of the census, arguing that standardized, clear, and statistical approaches and practices were carried out across all regions of America, the public at the time was disappointed in the national growth rate and suspected underenumeration. With especially bitter complaints coming from New York and Philadelphia claiming up to a third of the population was not counted, the President made the rare move to order a recount in those areas. While it was thought a large fraction of the population was not counted for being indoors in the wintry cold, newer estimates resulted in only a 2.5% increase in Philadelphia's population and a 2% increase in New York's.
This controversy of the 1870 undercount resurfaced in 1890, when the national growth rate between 1880 and 1890 was discovered to be much lower than it was between 1870 and 1880. Critics then asserted that the 1870 population must have been underenumerated by over 1.2 million people to account for the discrepancy between growth rates; it was presumed that the growth rate in 1880 had to be exaggerated because of the 1870 undercount. Despite the fact that modern investigations have yet to quantify the exact effect of the undercount, most modern social scientists do not believe the undercount was as severe as 1890 investigators assumed. Today most analyzers compare the 1870 undercount to the non-response rates seen in most modern census data.
^Munroe, James Phinney (1923) A Life of Francis Amasa Walker, Holt, p.111 Conditions for the work were therefore so adverse that the new superintendent (Walker), with characteristic frankness, repudiated in many instances the results of the Census, denouncing them as false or misleading and pointing out the plain reasons. p.113 When the appointments of enumerators were made in 1870 the entire lot was taken from the Republican party, and most of those in the South were negroes. Some of the negroes could not read or write, and the enumeration of the Southern population was done very badly. My judgement was that the census of 1870 erred as to the colored population between 350,000 and 400,000