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A Snapshot of the Nation
The official U.S. Census is described in Article I, Section 2 of the Constitution of the United States. It calls for an actual enumeration of the people every ten years, to be used for apportionment of seats in the House of Representatives among the states. The first official Census was conducted in 1790 under Thomas Jefferson, who was the Secretary of State. That census, taken by U.S. marshals on horseback, counted 3.9 million inhabitants. Since that time, the decennial Census has been conducted every ten years, generally on April 1 in years ending in a zero.
– The Census Bureau
Besides providing information needed for congressional and state legislative redistricting and distribution of funds for government programs, Census data are used in many other ways. Census data are used extensively in marketing applications, supplementing smaller surveys, cooking up estimate and projection numbers, helping scholarly researchers learn more about residents and neighborhoods and many other uses. Census data are available for many levels of geography, including states, counties, cities and towns, ZIP codes, census tracts (neighborhoods) and blocks. In Census 2000, there are a total of 114 geographic levels, and about 2.4 million potential variables down to Census Tract level. Given the vast amount and coverage of these data, it is easy to get lost in all these datasets.