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Redistricting is the process by which district maps for the U.S. House of Representatives, state legislatures, and local governing bodies are redrawn. These maps are used to determine the voting base for elected officials. The purpose of the redistricting process is to account for population change and to ensure that the governing body’s districts have roughly equal populations in compliance with the one person, one vote requirements of the U.S. Constitution.

Before redistricting can take place, a process called enumeration must take place in which the population of the entire country is counted via the Census. This occurs every 10 years. The apportionment or reapportionment process then determines how many seats in the U.S. House of Representatives each state is entitled to. The number of seats is based on the state’s population in relation to other states. Then, after receiving the results of the U.S. Census, redistricting takes place.

Each state is in charge of its own redistricting process, meaning that the process varies from state to state. For example, in some states, independent citizen commissions are charged with drawing the maps. In others, it is the legislature’s responsibility to draw maps. Further, some states prohibit considering political party in the redistricting process, while others go so far as to permit map drawing designed to protect incumbents.

Although states retain the freedom to determine who draws the maps and the criteria for doing so, there are several federal legal requirements that all district maps must meet. These include: having districts with substantially equal populations; districts that do not dilute the vote of communities of color; and districts that are not drawn with race as the predominate factor.

The following resource discusses some of the basics of redistricting, including the different bodies in charge of redistricting, common criteria that have historically been used to draw maps, and the federal legal requirements that district maps must meet.

Who Draws the Maps?

There are a variety of ways that states have and can conduct the redistricting process. States may have independent commissions, advisory commissions, political commissions, or the legislature draw maps. Some states even allow other groups that are not affiliated with or acting under the delegated authority of the state legislature that take charge and redraw district boundaries. Below is a description of some of the more typical bodies that can be tasked with redistricting.


Traditionally, the state legislature has been responsible for redistricting, and the majority of states adopt this approach. When the legislature is tasked with redistricting, those elected to the legislature during the redistricting cycle draw, approve, and pass the new maps. Legislatures generally train or hire technical staff to assist elected officials in the process due to the technical skill requirements needed to successfully redistrict.

The following states have their legislatures draw state legislative and congressional lines: Alabama; Delaware; Florida; Georgia; Illinois; Indiana; Kansas; Kentucky; Louisiana; Massachusetts; Minnesota; Mississippi; Nebraska; Nevada; New Hampshire; New Mexico; North Carolina; Oklahoma; Oregon; Rhode Island; South Carolina; Tennessee; Texas; Virginia; West Virginia; and Wisconsin. Vermont takes a similar approach, having its legislature draw state legislative lines with the advice of the Vermont Apportionment Board.

Independent Commission

Independent redistricting commissions are separate entities from the legislature and are in charge of redistricting. Independent Commissions may include citizens who are not current lawmakers or public officials. Eligibility requirements for serving on the commission, along with map drawing guidelines, vary from state to state.

Arizona, California, Colorado, and Michigan redistrict by independent commission. New York and Utah use independent commissions in their process, but do not cede complete authority—the commissions prepare maps for the legislature to consider, but they are not binding.

Political Commission

Political commissions are different from independent commissions. Political commissions consist of elected officials, lawmakers, and/or legislative staff. Commission members are typically appointed by or include the governor, legislators, or members of the state supreme court. Usually, elected officials can serve as members of the commission, and these commissions are generally bipartisan, but not always.

States with political commissions include: Arkansas; Missouri; New Jersey; Ohio; and Pennsylvania. Some states, like Texas, have a political commission draw maps if its Legislature fails to timely do so.

The Iowa Model: Nonpartisan Legislative Staff

Iowa has a unique approach to redistricting; nonpartisan legislative staff draw district boundaries through a nonpartisan approach. The legislature relies on an advisory commission to advise the legislature on drawing district lines. The legislative staff submits maps to the legislature, which the legislature then votes on. The legislature has the final say on which maps are adopted.

The Maryland Model: Governor’s Citizen Commission

In Maryland, the Governor submits a plan for the state legislative districts to the General Assembly. The Assembly must then adopt its own plan or the Governor’s plan by the 45th day of the regular legislative session. The Governor cannot veto this plan. If the Assembly fails to adopt a plan, the Governor’s plan becomes binding. Because the Maryland Constitution does not mandate a process for congressional redistricting, it has traditionally been carried out through the normal lawmaking process.

In the 2021 Redistricting Cycle, Governor Hogan will use an Independent Citizen Commission made up of Maryland voters from the two major parties and independent or nonpartisan voters to draw the state legislative districts. The Commission will also draw a congressional map that the Governor will submit to the Assembly for consideration. The Commission’s congressional map will not be legally binding on the legislature.