About this Guide
This research guide describes some of the major print and electronic resources for finding Census statistical information from the Decennial Census from 1790 to 2010. There is also information on the American Community Survey (ASC) and how to obtain statistical information. There is also information on Census tracts, Census tract numbers for Pittsburgh and Alleghany County, and mapping.
For further information on these resources or to schedule a research consultation, contact Mark Scott or Tom Twiss.
Why the Federal government takes a Census
According to the United States Constitution, Article I, Section 2 mandates that an apportionment of the representative among the states, for the U.S. House of Representatives, be carried out every 10 years (decennially).
Apportionment is the process of dividing the 435 seats in the U.S. House of Representatives among the 50 states. Using equal portions, each state is assigned one congressional seat (as provided by the Constitution). The apportionment formula then allocates the remaining 385 seats one at a time among the 50 states until all 435 seats are assigned.
Though the Census is taken for apportionment it is also important to help distribute billions of dollars annually in federal, state, local, and tribal funds. In addition the Census is used to draw state legislative districts, evaluate the success of programs, and identify populations in need of services.
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