MapMaker: 2020 United States Apportionment

MapMaker: 2020 United States Apportionment

The process to determine how many representatives each state receives in the United States House of Representatives is called apportionment.


9 - 12+


Geography, Human Geography, Social Studies, Civics, U.S. History

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When the founders of the United States established the government they wanted to ensure power was separated and there was a system of checks and balances. Therefore, the U.S. has three main branches of government: the executive branch (to carry out laws), the judicial branch (to examine laws), and the legislative branch (to create the laws).

The executive branch is led by the president who is elected by U.S. citizens 18 years and older every four years. The president nominates justices to the Supreme Court when it has vacancies because a justice steps down or dies. The Supreme Court has had nine justices since 1869. The president also nominates court of appeals judges and district court judges. All nominated judges are confirmed by the United States Senate, as stated in the Constitution. The president and members of Congress, or the legislative branch, both serve limited terms. Congress is composed of two parts: the Senate and the House of Representatives. The Senate is composed of 100 senators, two from each of the 50 states. U.S. territories and the District of Columbia are not represented in the Senate as they are not considered states. Each Senator serves a term of six years. The House of Representatives has 435 members determined by the population of each state. Territories are not represented in the House, but the District of Columbia has an “at-large” representative who may not vote on issues being considered. These members each serve a term of two years.

The process to determine how many representatives each state receives is called apportionment. Every 10 years, since 1790, the United States conducts a census to tally the total number of residents (citizens, noncitizens, deployed members of the U.S. Armed Forces, and federal civilian employees stationed abroad) in each state and gather some information about them and the nation’s economy. The U.S. Constitution establishes that each state must have at least one representative. The remaining 385 seats are then divided up based on the method of equal proportions, which was adopted by Congress in 1941. Title 13 of the U.S. Code requires the apportionment calculation must be completed and delivered to the president within nine months of the completion of the census.

This map layer was created with data from the United States Census Bureau 2020 census. The map shows which states have gained or lost representatives since the last apportionment completed in 2010.

Did the state you live in have a change in the number of people representing you in the House of Representatives? Do you know who your representative is?

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Sarah Appleton, National Geographic Society, National Geographic Society
Expert Reviewer
Anita Palmer
Last Updated

June 20, 2024

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