Reapportionment is the process re-distributing seats in the House of Representatives, or other legislative body, according to the population in each state. This example of reapportionment is actually done through a complex mathematical formula that ensures the most even distribution of House seats. While each state gets two seats in the U.S. Senate, each state is given a certain number of House seats based on its population; and every state is guaranteed at least one seat by the constitution, regardless of how many people live in that state. To explore this concept, consider the following reapportionment definition.

Definition of Reapportionment


  1. The redistribution of the representation in a ruling body.

Origin of Apportion

1565-1575       Middle French apportionner (to portion)

What is Reapportionment

Reapportionment is the official redistribution of representation in a ruling body, such as Congress. By Federal law, there are 435 total congressional districts that make up the House of Representatives. Every ten years, a census is taken of the United States’ population, and then the total number of American citizens is divided in order to determine how many people should be included in each congressional district.

This census is used as the standard for the following ten years until it is time for the next census to be taken. Those 435 congressional districts are then “apportioned,” or divided and assigned to each of the states as directed by the United States Constitution. Every state is guaranteed to be given at least one congressional district, regardless of how many citizens make up its population. The remaining districts are then allocated using a complex mathematical formula that divides up state representation as evenly as possible.

By law, the Secretary of Commerce is required to provide the President with the state population totals within nine months of the date the census is taken (“Census Day”). The President must then submit that apportionment to the Clerk of the House within five days after Congress resumes normal business activities in the New Year.

Reapportionment and Redistricting

The terms “reapportionment” and “redistricting” are often used interchangeably, though the two terms are, in fact, very different. Reapportionment and redistricting are both important in the choosing of congressional representatives. How they differ is in what, exactly, that they divide. While reapportionment refers to reassigning the number of House representatives each state may have, redistricting draws boundaries within each state for voting and representation, after reapportionment has taken place.

For example:

Reapportionment has designated that X State will have four seats in the House of Representatives. These representatives need to be elected by the state’s voters. For this purpose, X State is divided into four sections (called “districts”), which attempt to balance population in each district, rather than geographical area. One representative is then elected by each district. The next 10-year census may determine that X State have more or fewer representatives.

Therefore, the major difference between reapportionment and redistricting is that reapportionment refers to a change in the number of representatives a state is allowed, and redistricting refers to a change in voting boundaries within the state.


Gerrymandering is essentially an example of reapportionment or redistricting gone rogue. When states are permitted to draw district lines in such a way that favors one party over another, it is called gerrymandering. Gerrymandering is an underhanded tactic used to lower or eliminate the chances of the opposing party becoming significant competition. For instance, during redistricting, the people responsible for drawing the new district lines are encouraged to do it in such a way that each voting district contains more residents of their own party.

Some states actually prohibit their state officials from participating in redrawing district boundaries, and understandably so. However, even when politicians are not directly involved in the redrawing, they are still permitted to vote against any proposals with which they do not agree. As a result, even if those politicians do not directly influence the redrawing of the district boundaries, they can still control where and how the new district boundary lines are drawn, through the power of their votes, provided they belong to the majority party.

Formulas for Reapportioning Congressional Seats

Complex mathematical formulas are the meat of the reapportionment process. Four different formulas for reapportioning congressional seats to the states have been used since 1790, which shows just how much the system has evolved throughout history. These four formulas are as follows:

  • 1790 – 1840: Congress used what was called the “method of greatest divisors.” This formula divided the total number of citizens in the American population by the number of seats, then assigned each state a quota. The number of members was then adjusted so that each state was awarded the exact number of seats it was supposed to get based on the previously established quota.
  • 1842 – 1850: During this time, Congress used a different formula for reapportioning congressional seats, which was the “method of major fractions.” This formula provided each state with an additional member when its quota included a fraction exceeding one-half. The total number of members was then adjusted accordingly.
  • 1850 – 1910: The formula for reapportioning congressional seats used here was originally proposed by Alexander Hamilton. Here, members would be first apportioned according to their state’s quota, and any fractional remainders would be disregarded. Then, any leftover seats were issued to those states with the largest fractional remainders.
  • 1930 – Present Day: Congress now uses the “method of equal proportions.” This formula takes a state’s population and divides it by the mean number of that state’s current number of House seats and the next seat (the square root of n[n-1]). This formula takes the remainders among the states and allocates them in such a way as to provide the smallest difference between any pair of states in a district, and in the number of people assigned to each representative.

Reapportionment Act of 1929

The Reapportionment Act of 1929 was a combination census and reapportionment bill that was passed by Congress. In the bill, a permanent method was established for apportioning the set number of 435 seats that exist in the House of Representatives today by using decennial censuses. The Reapportionment Act of 1929 was simply a new bill, and it did not address the requirements that had been written into prior apportionment acts, which required that districts be adjoining and condensed, and that their populations be generally equal across the board.

The Reapportionment Act of 1929 was not meant to act as an authority insofar as congressional redistricting. All the Act was designed to do was establish a system that would guide the House in determining which seats would be reallocated to states that saw significant changes in their population during the 10-year censuses. However, because the Act did not offer suggestions on just how congressional district lines should be drawn, significant problems were an inevitable result.

For instance, the Act allowed states to make their own rules when it came to drawing districts, which meant that some districts were larger or smaller than others. The Act also provided for states to simply abandon the idea of drawing districts altogether, with those states choosing instead to elect representatives as a whole. States that elected to do just that include New York, Hawaii, and Washington.

Reapportionment Example in a State Legislature

In 1961, voters in Jefferson County, Alabama, challenged the apportionment in their state, when it became clear how unfairly the district lines had been drawn. The state’s constitution specified that each county would have a single Senator in the state legislature, regardless of the number of residents. Because of the differences between urban and rural counties, one district had, at that time, 41 times the number of another. In this example of reapportionment gone bad, a group of citizens sought to have the glaring injustice remedied.

By filing a civil lawsuit, this group of Alabama voters complained that the “malapportionment” of voters effectively stripped them and others like them of their rights under the Equal Protection Clause of the Fourteenth Amendment and the Alabama Constitution. They asked that the state’s apportionment and districting methods be declared unconstitutional, alleging discrimination against voters who lived in counties with populations that had grown considerably larger since the 1900 census was taken.

The question then became whether or not Alabama’s apportionment methods violated the Fourteenth Amendment’s Equal Protection Clause by demanding that there should be at least one representative per county. Also questionable was the fact that Alabama created a senatorial district for every senator with no regard for potential changes in population.

In this case (Reynolds v. Sims), the U.S. Supreme Court ruled in favor of the plaintiffs, holding that the Equal Protection Clause demanded exactly what it said it would: that state legislative representation should be equal across the board for all of the citizens within that state. States were required by law to exercise “honest and good faith” attempts at constructing districts that were as equal in population as they possibly could be.

Other States with Unfair Apportionment

Prior to the Supreme Court’s ruling in the Reynolds case, a number of other states had unfair apportionment and districting practices. These included:

  • Connecticut – One House of Representatives district had only 191 residents.
  • Idaho – The smallest Senate district had 951 residents, while the largest had over 93,000
  • California – One member of the state Senate represented 6 million people (in Los Angeles County), while another member represented 14,000 people in his rural county.
  • New Hampshire – One House Representative’s district had only 3 voting residents, while another had more than 3,200.
  • Nevada – The 17 state senators represented as few as 568 people, and as many as 127,000.
  • Utah – Members of the state legislature represented as few as 165 people, and as many as over 32,000 people.
  • Vermont – The largest district was comprised of 35,000 people, the smallest just 36 people.

Related Legal Terms and Issues

  • Census — An official survey of a population, typically recording details about those living in a particular community.
  • Decennial – Something that occurs every 10 years.