Who Draws the Maps? Legislative and Congressional Redistricting

Every ten years, states redraw their congressional and state district lines. Each state determines for itself, usually detailed in the state constitution, who will draw district lines for state legislators and Congress members.

April 14, 2017

The way lines are redrawn can influence who can win the next election and affect the balance of political power, which communities are represented, and what laws are passed. Unfortunately, that power means the process also can be abused. Litigation in a number of states currently is challenging the drawing of maps based on race or partisanship or failure to comply with other legal requirements.

However, the past twenty years also have seen significant growth in efforts to fix the process. While the vast majority of states continue to use the state legislature for drawing districts, there is a growing trend for states to use alternative approaches to mapdrawing. Citizen-driven ballot initiatives sparked redistricting reform in Arizona in 2000 and in California in 2008 and 2010. Since then, New York in 2014 and Ohio in 2015 also have adopted various types of reforms.

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

State Legislature

In most states, the state legislature passes redistricting plans as regular legislation: the plan has to be approved with a majority vote in each chamber and is subject to veto by the governor. However, some states have different provisions. CT requires a plan to be passed with a 2/3 majority vote. Legislative plans in CT, FL, MD, and MS are not subject to gubernatorial veto. Neither legislative nor congressional plans are subject to a gubernatorial veto in CT and NC.

Most states have a deadline for drawing district lines set by the state constitution.  If the legislature can’t agree on a map before the deadline, state or federal courts may step in to make sure that the district lines are set before the next election.  Courts also sometimes draw maps of their own to remedy legal violations in maps passed by the legislature. A handful of states, likewise, use backup commissions in case of a deadlock (more below on backup commissions). 


Advisory Commission

Advisory commissions, which may consist of legislators or non-legislators, or a mix, recommend redistricting plans to the legislature. The legislature has the final say in approving district maps, usually by an up or down vote. Maine requires a plan to be passed with a 2/3 majority of the legislature.

Six states have an advisory commission in place for either congressional or state legislative districts, or both. In some cases, the advisory commission is established by the state's constitution. In other cases, such as Iowa, a state will set up an advisory commission by statue. In Iowa, a nonpartisan bureau draws draft lines for the legislature to accept or reject as is; only after the legislature has rejected two sets of plans can it draw districts as it pleases.  So far, the Iowa legislature hasn’t used its authority to drawn its own maps from scratch.

Backup Commission

A backup commission draws the map only when the legislature is deadlocked or when the governor vetoes the proposal. Six states use a backup commission for legislative plans and two for congressional plans.

In CT, IL, and OK, the backup commission is made up of people selected by the legislative leadership.  In MS and TX, the backup commission is made up of specific statewide elected officials, like the state treasurer or state attorney general. In MD, the governor’s proposal becomes the default plan if the legislature fails to approve its own map.

Independent Commission

Six states use an independent commission, comprised of members who are neither public officials nor current lawmakers.  Legislators may have a role in selecting the commissioners, but do not serve on the commission. These six states also prevent commissioners from running for office in the districts they draw, at least for a few years after they draw the lines. Together, the restrictions on who can be a commissioner and the restrictions on running for office mean that even though legislators may have a role in picking commissioners, neither legislators nor candidates draw their own district lines themselves.


Politician Commission

Seven states use a politician commission to draw congressional and/or legislative districts.

Each politician commission is designed differently. AR, HI, and MS use a commission where all members are incumbent lawmakers or other elected officials to create redistricting plans. Four states – CO, NJ, OH, and PA –  use commissions with a mix of elected officials and non-politician members, usually appointed by the legislative or party leadership, the governor, or chief justice of the state supreme court.

Single Congressional District States

Seven states currently have only one congressional district.