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Who Draws the Maps? Legislative and Congressional Redistricting

A guide to who controls the redistricting process in all 50 states.

  • Brennan Center for Justice
Published: January 30, 2019

Every ten years, states redraw the bound­ar­ies of their congres­sional and state legis­lat­ive districts after the census. Who does the line draw­ing varies state by state.

The way districts are drawn can have a big impact on both voters and politi­cians. It can influ­ence who wins elec­tions, how polit­ical power is distrib­uted, which communit­ies are repres­en­ted, and what laws are passed. This creates a power­ful incent­ive to manip­u­late district lines for polit­ical gain. And over the last two decades, these manip­u­la­tions have grown increas­ingly common and soph­ist­ic­ated.

However, recent years have seen a signi­fic­ant growth in efforts to protect the redis­trict­ing process from abuse. While the vast major­ity of states continue to let their legis­latures draw districts, there is a grow­ing move­ment toward altern­at­ive approaches to mapdraw­ing. Citizen-driven ballot initi­at­ives let to the passage of redis­trict­ing reforms in Arizona in 2000 and in Cali­for­nia in 2008 and 2010. Since then, voters in Color­ado, Michigan, Missouri, New York, Ohio, and Utah have also adop­ted changes to improve the redis­trict­ing process. 

With another round of redis­trict­ing in 2021, many state legis­latures are currently consid­er­ing redis­trict­ing reforms. Visit our Redis­trict­ing Reform Tracker for inform­a­tion on redis­trict­ing bills currently pending before legis­latures.

The follow­ing maps show who is currently respons­ible for redis­trict­ing in the United States

State Legis­lature

State legis­latures currently are respons­ible for draw­ing congres­sional districts in 31 states and state legis­lat­ive districts in 30.

In most states, the legis­lature passes redis­trict­ing plans as regu­lar legis­la­tion. Plans often must be approved with a major­ity vote in each cham­ber and are subject to veto by the governor, but a few states exclude the governor from the process. State legis­lat­ive plans in Flor­ida, Mary­land, and Missis­sippi are not subject to gubernat­orial veto. In North Caro­lina, neither congres­sional nor state legis­lat­ive plans are subject to gubernat­orial veto.

Advis­ory Commis­sion

Four states use an advis­ory commis­sion to draw congres­sional plans, and six states have an advis­ory commis­sion to draw state legis­lat­ive districts.

Advis­ory commis­sions, which may consist of legis­lat­ors or non-legis­lat­ors or a mix, recom­mend redis­trict­ing plans to the legis­lature. The advis­ory commis­sion draws the maps, then the legis­lature has the final say in approv­ing them, usually by an up or down vote. Connecti­cut and Maine require a plan to be passed with a 2/3 major­ity of the legis­latures, and in Connecti­cut, the plan is not subject to gubernat­orial veto.

Inde­pend­ent Commis­sion

Four states use an inde­pend­ent commis­sion for both congres­sional and state legis­lat­ive districts.

Inde­pend­ent commis­sions are made up of members who are neither public offi­cials nor current lawmakers and are selec­ted with the help of a screen­ing process that is conduc­ted by an inde­pend­ent entity. Commis­sion­ers are respons­ible for draw­ing and approv­ing the final maps.

Polit­ical Appointee Commis­sion

Four states use a polit­ical appointee commis­sion for congres­sional plans, and nine states use this type of commis­sion for state legis­lat­ive plans.

Polit­ical appointee commis­sions are composed of indi­vidu­als who are directly appoin­ted by elec­ted offi­cials, party lead­er­ship, or polit­ical party commit­tees. In some states, the member­ship of a polit­ical appointee commis­sion is evenly divided between parties, while others allow members of one party to hold more seats on the commis­sion than the other. Ohio uses a hybrid between a polit­ical appointee commis­sion and a politi­cian commis­sion to draw its state legis­lat­ive districts.

Politi­cian Commis­sion

One state, Arkan­sas, uses a politi­cian commis­sion for state legis­lat­ive districts.


Politi­cian commis­sions are comprised entirely of incum­bent lawmakers or other elec­ted offi­cials, usually appoin­ted by the legis­lat­ive or party lead­er­ship, the governor, or chief justice of the state supreme court.

Backup Commis­sion

Three states use a backup commis­sion for congres­sional plans and five for state legis­lat­ive plans.

Backup commis­sions are called on to draw maps when the legis­lature is dead­locked or when the governor vetoes the proposal. Ohio’s backup commis­sion draws the congres­sional map if the legis­lature fails to pass a plan with bipar­tisan support.

Single District States

Seven states currently have only one congres­sional district.

Follow­ing the 2020 Census, however, Montana may gain one congres­sional seat. In that case, the state’s polit­ical appointee commis­sion will draw both congres­sional and state legis­lat­ive lines in 2021. Rhode Island may lose one of their two seats, becom­ing a single district state.