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2010 apportionment map
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Apportionment of the U.S. House of Representatives
based on the 2010 Census

Apportionment is one of the most important functions of the decennial census. Apportionment measures the population so that seats in the U.S. House of Representatives can be correctly apportioned among the states. Until the middle of the twentieth century, Congress enacted new apportionment legislation following almost every census.

The Constitution does not specify a certain method of apportionment. Almost as soon as the first census was completed in 1790, political thinkers, including Alexander Hamilton and Thomas Jefferson, began suggesting their own methods. The plans generally differed according to whether they favored the large or small states in post-census allocation of representatives. This disagreement over method of apportionment resurfaced every ten years until a permanent method was set following the 1940 census.

In this section, you'll find a collection of legislation dealing with apportionment, as well as an explanation of the methods of apportionment that have been used to allocate seats in the U.S. House of Representatives.

Read more about the history of apportionment in a draft paper H. Peyton Young delivered during a March 2004 Census Bureau symposium, Fairness in Apportionment [PDF 917 KB].

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Source: U.S. Census Bureau | Census History Staff | Last Revised: July 23, 2015