Last revised: August, 2008
Census Information and Data
Scope: This is a guide to census information and data collected and produced by the U.S. federal government. If you have any questions or would like further assistance, please contact the U.S. Government Information, Maps & GIS Services Staff at govdocs@umd.edu or 301.405.9165.
Table of Contents
Overview of the Decennial Census
What Is the Decennial Census?
A census is an official count of a population. The first national census in the United States was taken in 1790 and, since the U.S. Constitution requires that a census be taken every ten years, it's referred to as the "decennial census." For more information on the census, see the Census Bureau's History page, Historical Background of the United States Census, or the following books:
- Anderson, Margo J., ed. Encyclopedia of the U.S. Census. Washington, D.C.: CQ Press, 2000.
LOCATION: UMCP McKeldin Library, US Government Information Reference
CALL NUMBER: HA37.U55 C66 2000 - Hinckley, Kathleen W. Your Guide to the Federal Census for Genealogists, Researchers, and Family Historians. Cincinnati: Betterway Books, 2002.
LOCATION: UMCP McKeldin Library, US Government Information Reference
CALL NUMBER: HA37.U6 H556 2002 - Wright, Carroll D. The History and Growth of the United States Census, Prepared for the Senate Committee on the Census. Washington, DC: Government Printing Office, 1900.
LOCATION: UMCP McKeldin Library, US Government Information SU Docs
CALL NUMBER: Y 4.C 33/2:H 62
Why Is It Taken?
The original purpose of the census was to determine apportionment of Congressional representatives. The government was also interested in determining the military potential of the country (thus the question about the number of males over age 16). While it is still used for apportionment purposes, it also serves to collect data used to manage or evaluate government programs. For example, the data may be used to help with transportation planning, identifying needs for childrens' services, or distributing funds for community development.
How Is It Taken?
During the first few censuses, U.S. marshals and their assistants, or enumerators, canvassed the country counting people in each household. In fact, until 1960, when the census was first mailed to households, it was taken door-to-door.
The census is now taken using two different forms. The "short-form", which is sent to every household, asks a few basic questions that cover relationship to head of household, type of dwelling, sex, age, and race. The "long-form", which is sent only to a sample or percentage of the population, asks more in-depth questions, for example, educational attainment, ethnic origin, and income. Data obtained from the long-form is weighted to represent the total population. The American Community Survey, first conducted in 1996 in select geographic areas, asks the same type of questions that are found on the long-form. As an ongoing survey, it provides more current data on a more frequent basis and will take the place of the long-form in the 2010 census. Read this guide, A Compass for Understanding and Using American Community Survey Data: What General Data Users Need to Know [pdf] for more information.
Measuring America: The Decennial Censuses From 1790 to 2000 contains copies of the census questionnaires used from 1790 to 2000, as well as information on instructions given to enumerators. For additional information, see How the Census Works.
1930 census enumerator visiting a household
Source: U.S. Census Bureau
What Type of Information is Collected?
The decennial census now focuses on demographic characteristics of the population characteristics and is often referred to as the "Census of Population" or the "Census of Population and Housing." Historically, other types of information have been collected about areas such as agriculture, mining, or manufacturing. Now, many of those areas are subjects of their own censuses (see Agriculture, Economic, Governments) or surveys.
The chart from Measuring America, Population Items on Principal Census Questionnaires, lists which characteristics were measured in each census so you can track changes in coverage over time.
What Geographic Areas Are Covered?
The geographical areas covered by the census have developed over the years. The basic geographical areas that have been measured over the years include the nation, states and counties. Census tracts, the smallest geographical unit measured, were created for select cities in 1910 but not included in census publications until 1940. In 1990, census tracts were expanded to cover all counties; prior to that they covered only metropolitan and other heavily populated areas. Maps of census blocks and tracts can be found with the decennial census publications. It is important to note that only data from the short-form is available at the census block level. More detailed data can be found at the block group level. More information on census geography can be found in the Geographic Areas Reference Manual.
Census Bureau Geographic Hierarchy
Source: U.S. Census Bureau, Geography Division
Census Publications and Data in the UM Libraries
Returns/Schedules
The census returns, or population schedules, are the actual forms filled out by enumerators. They include names, ages, marital status, places of birth, and occupation, depending on the year. For reasons of privacy, these schedules are not released to the public until 72 years after they are taken. UM Libraries have copies of the population schedules for Maryland from 1790-1930. They are available in the Maryland Room, in Hornbake Library. Population schedules for other states can be accessed at the National Archives in D.C. or contact your public library to see if they have access to the Ancestry.com or HeritageQuest subscription databases.
Decennial Publications
After each census, the data was tabulated and disseminated in several series. The Census Bureau is in the process of digitizing these series and many of them are now available on the Census of Population and Housing page. (Note: Census pdf files do not open with Internet Explorer.) They can be found in print format in UM Libraries' U.S. Government Information Collection, on the 4th floor of McKeldin Library. Here's a list of call number locations for each decennial census:
| Census Year | Call Number (SU Docs) |
| 1790-1840 | Ask at 1st floor Information Desk |
| 1850-1900 | Begins at I 8.5: |
| 1910 | C 3.16: |
| 1920 | C 3.28/5: |
| 1930 | C 3.37/5: |
| 1940 | C 3.940: |
| 1950 | C 3.950: |
| 1960-2000 | C 3.223/ (various series) |
Inventory of U.S. Census volumes held by U.S. Government Information & GIS Services, 1790-1920 [pdf]
Other Publications
Besides the main decennial census publications, the Census Bureau often publishes special subject analyses using decennial census data or reports from other surveys taken in-between decennial censuses. Examples include periodic publications like Negroes in the United States and Religious Bodies, or series like Current Population Reports. These publications can be identified through the Libraries' Catalog, searching for your topic using "census" as a keyword or limiting to "Bureau of the Census" as author, or by using one of the print resources. Many can be found on the 4th floor of McKeldin Library at U.S. Government Information SU Docs C 3.2: and some are available online on the Census Bureau's Special Collections page, which can be accessed by subject using the University of Colorado, Boulder's Index to Census Digitized Special Collections. (Note: Census pdf files do not open with Internet Explorer.)
Data
For more recent censuses, data is available online or on CD-ROM/DVD, formats which allow users to download and manipulate the data. UM Libraries has commercial CD's that cover the 1970-1990 censuses. They can be used both to access and download large quantities of data, or with GIS software. There are also a number of Census Bureau CD's from the 1990-2000 censuses. They can be found by searching the Libraries' Catalog. Use the Advanced Search option and choose "Electronic Resources (discs)" from the format drop-down menu. Ask at the 1st floor Information Desk to access any CD-ROM or DVD.
Much of the online data can be accessed through the Census Bureau's data portal, American Factfinder. Data is available back to 1990. Learn more with American Factfinder Tutorials. The Census Bureau also provides other Data Access Tools.
Data may also be found online through the Inter-University Consortium for Political and Social Research (ICPSR). This resource has many data sets containing census data. UMCP faculty, students and staff may access the data by contacting the Office of Academic Computing Services in the College of Behavioral and Social Sciences (BSOS). Members of BSOS may access the data for free; others must pay a fee.
Resources for Finding Census Information
Online Resources
- American Factfinder (Census Bureau)
http://factfinder.census.gov
Census Bureau portal to census data from approx. 1990-present. - County and City Databook (Census Bureau)
http://www.census.gov/statab/www/ccdb.html
Detailed tables of Census data broken down by county and city. 2000 and 2007 versions available. Note: Census pdf files do not open with Internet Explorer. - Decennial Censuses: 1790-2000 (Census Bureau)
http://www.census.gov/prod/www/abs/decennial/index.htm
Links to 1790-2000 decennial census publications as well as publications from other censuses, in PDF format. Note: Census pdf files do not open with Internet Explorer. - Historical Census Browser (University of Virginia Libraries)
http://fisher.lib.virginia.edu/collections/stats/histcensus/
Selected census data for each state and county from 1790-1960. - Historical Statistics of the United States (UM only)
Basic historical federal statistics back to the 1700's - Index to Census Digitized Special Collections (University of Colorado, Boulder)
http://ucblibraries.colorado.edu/govpubs/gd/censusindex.htm
Access, by topic, to documents available online from the Census Bureau. - Maryland State Data Center
http://www.mdp.state.md.us/msdc/
Access historic and current census data and analyses from the "Census Data" link. - Selected Historical Decennial Census Population and Housing Counts (Census Bureau)
http://www.census.gov/population/www/censusdata/hiscendata.html
Links to a number of reports on historical trends. - Statistical Abstract of the United States (Census Bureau)
http://www.census.gov/compendia/statab/
Digest of major statistics from many U.S. agencies including the Census Bureau since 1878. - Subjects Index (Census Bureau)
http://www.census.gov/main/www/subjects.html
Find Census Bureau guides to a variety of surveys and topics, such as age, race, and poverty.
Print Resources
- American Statistics Index (ASI). Annual. 1974 - .
Comprehensive index to U.S. federal statistical publications, including those of the Census Bureau. See the American Statistics Index guide. The publications can be found in the U.S. Government Information collection on the 4th floor of McKeldin or the ASI microfiche collection in the 4th floor Computer, GIS and Microforms Lab.
LOCATION: UMCP McKeldin Library, US Government Information Reference
CALL NUMBER: Z7551.A4 - Cook, Kevin L. Dubester's U.S. Census Bibliography with SuDocs Class Numbers and Indexes. Englewood, CO: Libraries Unlimited, 1996.
An annotated bibliography of decennial census publications and other censuses from 1790-1945. Includes subject, SU Docs number, and title indexes.
LOCATION: UMCP McKeldin Library, US Government Information Reference
CALL NUMBER: HA214 .C66 1996 - County and City Databook. Irregular. 1949 - .
Tables of Census data broken down by county and city.
LOCATION: UMCP McKeldin Library, US Government Information SU Docs
CALL NUMBER: C 3.134/2:C 83/2/ - Historical Statistics of the United States. Washington, D.C.: Bureau of the Census, 1975.
LOCATION: UMCP McKeldin Library, Reference Stacks
CALL NUMBER: HA202.B87 1975. - Schulze, Suzanne. Population Information in Nineteenth/Twentieth Century Census Volumes. 3 volumes. Phoenix: Oryx Press, 1983/1985/1988.
Lists the table contents of each decennial census volume by subject and geography.
LOCATION: UMCP McKeldin Library, McKeldin Reference and U.S. Government Information Reference
CALL NUMBER: HA 214.S38 and HA 214.S39 - Statistical Abstract of the U.S. Annual. 1878 - .
Digest of major statistics from many U.S. agencies including the Census Bureau.
LOCATION: UMCP McKeldin Library, US Government Information Reference
CALL NUMBER: C 3.134:
