Counting people is one of the oldest activities of government. Some form of census taking has been employed in civilizations going back as far as Babylonia of 3800 B.C. and ancient China, usually by rulers who wanted to raise an army or impose taxes.
The word census originally referred to a Roman register of adult male citizens and their property, which determined political status, military obligation and taxation. Instituted by Servius Tullius, sixth King of Rome, about 550 B.C., Caesar Augustus eventually extended it to take in the entire Roman Empire. Thus the New Testament tells that Mary and Joseph traveled to Bethlehem to be counted among the descendants of David, in response to a decree that "all the world should be taxed."
Census records are compilations of information about individuals and their households. Numerical summaries of the various categories investigated are called "enumerations." These come at the end of some of the sections in census records, listing the total numbers of males, females, occupations, houses, etc., found in a small political division.
A federal population census has been taken in the United States every 10 years since 1790. However, a new law passed in1976 calls for censuses to be taken every five years, because the American people have become so mobile that modern census statistics go out of date very quickly.
The records of all but two of the American censuses have survived virtually intact to the present day. The 1890 census was almost totally destroyed by fire, only fragments, including a list of widows of Civil War pensioners, remain. Some parts of the 1790 census were destroyed but have been reconstructed from tax lists of the period. Smaller portions of the 1800 and 1810 censuses were destroyed during the War of 1812, and there are no surviving census records for New Jersey before 1830. On the whole, however, America's census records are more complete over a longer period than those of most nations.
The U.S. Government initiated the census to help apportion taxes and legislative representation among the states. In 1790, federal marshals rode out with a list of six sample questions. Over the years, as the government has made the census a tool for social planning, it has grown into an extensive survey of detailed information about the American people that's invaluable to genealogists.
Towns posted early censuses publicly in order to facilitate corrections or additions. Beginning in 1850, however, the government declared the information contained in the censuses confidential in order to ensure the greatest possible accuracy in responses. Although no law has yet been passed concerning the sealing of these records, an informal agreement between the National Archives and the Census Bureau in 1952 called for their release after 72 years. Today, only the censuses conducted through 1936 are available to the general public. The Census Bureau opened the 1900 census on a limited basis in 1975. Only genealogists researching their own family lines or authorized by another family to do research for them can consult its relevant sections. Also, genealogists may obtain some information about individuals listed in later censuses under special circumstances.
The value of census records to the genealogist varies according to the date of the record, since they aren't consistent in content. Congress stipulated that information should be furnished by the head of the family, recognizing the head of the family as the husband or father unless he was deceased. Because husbands and fathers are usually poor sources of ages and birth dates within a household, this led to numerous inaccuracies.