(April 2009) At the fractious Constitutional Convention in Philadelphia in 1787, America's founders conceived the idea of a national census to determine the number of representatives each state would send to Congress. The initial plan was to ensure no more than one representative for every 30,000 free persons. A slave counted for three-fifths of a free person.1

The idea of a complete population enumeration was not new—the ancient Romans conducted censuses to assess taxes, for example, and William the Conqueror ordered a census of people and property in England and Wales in 1086, which was recorded in a "Domesday Book"—but the United States was just the second Western country (after Sweden) to conduct a complete census. Most previous censuses were conducted for military and taxation purposes, while the U.S. census was initiated as part of a revolutionary system of representative government.2

Just as the form of government hammered out at the Philadelphia convention has withstood more than two centuries of tumultuous change, the tradition of the decennial population census has also endured. The United States has conducted a census every 10th year beginning with 1790. Except during the 1920s, the results were used to reapportion state representation in the U.S. Congress once a decade, and eventually for assessing taxes, gauging potential military strength, and a myriad of other purposes.

The Survey Questions

The first U.S. census was conducted by 16 U.S. marshals and their 650 assistants. It took them 18 months to visit households and compile the final tally of 3.9 million people, including nearly 700,000 slaves.

The census questionnaires have changed every decade—in most cases the changes involved requesting more detail, but sometimes the changes simply reflected the prevailing social and political currents. The 1830 Census collected information on whether people were deaf and blind; the 1840 Census added columns to identify "insane" or "feeble-minded" people (later dropped).3 It was also the first to ask whether people could read or write—to gauge the literacy levels of the population. The 1860 Census was the last to mention slaves, but later questionnaires requested separate information on household servants.4

Questions about color or race have been different in every census. The words and categories chosen each time paint a fascinating and revealing picture of how the concept of race has evolved over two centuries. In the past, race was understood as a biological concept. Today, most social scientists agree that race and ethnicity are social constructions and that humans cannot be classified by race according to biological factors. Instead, certain physical characteristics, such as skin color, are used to separate people into racial categories defined by society.

The number of racial categories used in the census has fluctuated considerably over the years. Groups identified by geography (for example, Asians, Pacific Islanders, and Aleutian Islanders) have been listed as races, together with racial groups defined by skin color (blacks and whites). Data on people with varying degrees of white and black ancestry have also been collected by previous censuses. And the racial categorization of nationality groups is changeable. Asian Indians were included in the white race in the 1970 Census but were counted in the Asian and Pacific Islander category starting with the 1980 Census.5 Enumerators for earlier censuses were instructed to report a person’s race based on observation. Since 1960, people have identified their own race, and that of others in their household, on census forms they fill out themselves. In 2000, for the first time, Americans were given the additional choice of marking all “race” categories with which they identified—a practice that will continue in 2010.

Only a few items on the census forms are required by law. The first census recorded limited information about the age, sex, and race of household members. Slaves were counted separately and were assumed to be black.

Census forms got longer in subsequent censuses as more questions were added. The Census Bureau eventually introduced the use of more than one questionnaire—one for the majority of Americans that asked just the handful of questions required for congressional reapportionment, and longer forms sent to a sample of households that asked additional questions about housing characteristics, birthplace, education, occupation, recent change of residence, mother tongue, and other items.

The 2000 Census asked just six questions on the basic "short form" that went to about 83 percent of U.S. households: age, sex, race, Hispanic origin, household relationship, and owner/renter status. The "long form," in 2000, with these six questions and 46 additional items, was the shortest since the 1940 Census. It was mailed to a sample of about 17 percent of households nationwide.

Adjusting to a Changing Country 

The way the government conducts the census has evolved from nonstandard forms filled out by a handful of federal marshals and their assistants in each state to a computer-readable questionnaire mailed to a painstakingly prepared address list of every housing unit in the United States. The early censuses were not highly precise and took months to administer. Special enumerators were not used until the 1880 Census, and the Census Bureau did not become a permanent government department until 1902.

Over the years, the U.S. census has both benefited from and spurred technological advances in statistical sampling, operational methods, tabulation technologies, and information systems. Punch cards that could be counted mechanically—an innovation that played a role in the development of electronic computers—were first used in tabulating the 1890 Census. The system was created by R. Herman Hollerith, a former employee of the Census Bureau who co-founded the company International Business Machines (later known as IBM) in 1911. The Census Bureau pioneered the use of computers for mass data processing.6

The changes in the procedures for collecting and disseminating census data reflect the country’s growth and westward expansion as well as technological changes. During the first century of census-taking, the country’s population soared from 3.9 million clustered along the eastern seaboard in 1790 to 63 million spread across the continent in 1890 (see figure). Census-takers realized they were chroniclers of American history. The official report from the 1890 Census begins: "This census completes the history of a century of progress and achievement unequaled in the world's history. The century has witnessed our development into a great and powerful nation." The report called the Atlantic states of the early United States the "sources of supply of a great westward migration. Their children have peopled the great interior valley and the mountains of the west...They have swarmed from the Atlantic coast to the prairies, plains, mountains, and deserts by the millions during the last century."7

US Resident Population

That first century of census-taking also saw the growth of cities and urban life. In 1790, just 5 percent of the U.S. population lived in cities and the overwhelming majority worked in agriculture. New York was the nation’s largest city with 33,131 residents; Philadelphia was close behind with 28,522. Only four other cities had as many as 8,000 people. By 1890, more than one-third of the U.S. population lived in urban areas; nearly one-half worked in manufacturing, trade, transportation, mining, or service industries. New York was still the largest city, with 1.5 million people, but scores of small and medium-sized cities had grown up along major transportation routes throughout the country. The census also documented a decline in the average household size during the 19th century, from about six to about five people, and an increase in the median age of the population from roughly 16 years to 22 years.

The second century of census taking recorded the phenomenal increases and diversification of the U.S population during the 20th century. Advances in modes of transport, communications, and industrial production helped transform where and how people lived and worked, and massive immigration at the beginning and end of the century infused new ethnic variety into the resident population. The 1920 Census was the first to document the shift from a rural to an urban majority. Politicians from predominantly rural states feared a loss of power to states with large and growing cities and blocked the reapportionment of electoral votes after the 1920 Census. The conflict between the smaller, rural states and larger, more urban states also reflected unease with the influx of millions of immigrants from southern and eastern Europe in the early 1900s. Congress restricted immigration in the 1920s in an attempt to prevent further shifts in the ethnic makeup of the U.S. population.8

The Ever-Increasing Costs

As the total population count soared from 76 million in 1900 to more than 281 million by 2000, the costs of conducting the decennial census rose from about 16 cents per person to more than $16 per person.9 The mailout/mail-back questionnaires, first used extensively in the 1960 Census, drastically cut back the need for enumerators to go door to door. In 2000, questionnaires were mailed to nearly all households, yet the Census Bureau still employed nearly 1 million part time workers to help carry out the 2000 Census. Enumerators visited some 12 million households that did not mail back a census questionnaire, and other Census Bureau employees scanned more than 1.5 billion pages of questionnaires. The 2000 Census cost about $4.5 billion, but the 2010 Census is projected to be the most expensive ever at approximately $14 billion. While the population is projected to increase by about 10 percent between 2000 and 2010, the cost of the next decennial headcount is projected to increase by 211 percent (see table).

United States Population and Cost of the Census

Census Population % Increase From Previous Census Cost % Increase From Previous Census
1950 151,325,798 14.9% $91,462,000 35.4%
1960 179,323,175 18.5% $127,934,000 39.9%
1970 203,302,031 13.4% $247,653,000 93.6%
1980 226,542,199 11.4% $1,078,488,000 335.5%
1990 248,718,301 9.8% $2,492,830,000 131.1%
2000 281,421,906 13.1% $4,500,000,000 80.5%
2010* 310,233,000 10.2% $14,000,000,000 211.1%

* These are estimates for 2010 provided by the U.S. Census Bureau.
Source: U.S. Census Bureau.

The Biggest Change Happens in 2010

In 2010, the Census Bureau is ushering in the most substantial change in the decennial census in more than 60 years. The 2010 census will use only a short-form questionnaire that will be sent to all housing units. The long-form questionnaire in 2010 will be replaced by a new survey called the American Community Survey (ACS). The ACS is a nationwide, continuous survey designed to provide communities with reliable and timely demographic, housing, social, and economic data every year, rather than only once every 10 years like the decennial long form. The ACS is also conducted by the Census Bureau. For more information about the ACS, see PRB's "About the American Community Survey".


  1. Margo J. Anderson, The American Census: A Social History (New Haven, CT: Yale University Press, 1988): 7-18.
  2. United Kingdom Office of National Statistics, "Census Taking Through the Ages," Factsheet 8, accessed online at www.statistics.gov.uk/census2001/pdfs/factsheet8.pdf, on April 15, 2009.
  3. U.S. Bureau of the Census, "Population and Housing Inquiries in the U.S. Decennial Census, 1790-1970," Working Paper 39 (Washington, DC: U.S. Bureau of the Census, 1973): 5-39.
  4. For more information about the history of the decennial census and questionnaire items, see Measuring America: The Decennial Censuses from 1790 to 2000, available online at www.census.gov/prod/www/abs/ma.html.
  5. Sharon M. Lee, "Using the New Racial Categories in the 2000 Census," A KIDS COUNT/PRB Report on CENSUS 2000 (Washington, DC: The Annie E. Casey Foundation and the Population Reference Bureau, 2001).
  6. Harvey Choldin, Looking for the Last Percent (New Brunswick, NJ: Rutgers University Press, 1994): 11-13.
  7. U.S. Bureau of the Census, 1890 Census (Washington, DC: Government Printing Office, 1897).
  8. Anderson, The American Census: 131-59.
  9. Bryant Robey, "Two Hundred Years and Counting: The 1990 Census," Population Bulletin 44, no. 1 (Washington, DC: Population Reference Bureau, 1989): 4-6.