Frequently asked questions

1What is gerrymandering?

Gerrymandering is drawing election districts to decide who wins before anyone votes. Whoever draws the map can see where each party’s voters live and shape districts around them: pack one side’s voters into a few districts they win by huge margins, or crack them across many districts where they always fall just short. Every vote is counted honestly, but the result was settled when the lines were drawn.

It isn’t one party’s trick. Anyone who draws the lines while seeing where voters live can do it, and the same tools can protect incumbents or split a community so its voice is lost.

2How do you stop gerrymandering?

Take the choice of lines away from people. If nobody picks where a line goes, nobody can pick it to help a party. Fair Maps does this with one fixed rule: split the state along the shortest line that divides its people evenly, repeat until each piece is one district, then even out the population block by block.

The rule sees only census headcounts and the shapes of census blocks. It never sees party, past votes, race, or where officeholders live, so it can’t favor anyone. It runs the same way in every state, and anyone can rerun the code and get the identical map. See How it works.

3How are districts drawn today?

In most states the state legislature draws new lines after each census, and the governor can usually sign or veto the map. Some states give the job to a commission. Either way, people choose where every line goes, and they can see where voters live while they do it. That is the opening gerrymandering needs.

Fair Maps shows the alternative side by side. Turn on “Compare with” on any state’s map to see today’s lines over the rule-drawn ones.

4Why does my district look strange?

A strange shape is not a mistake. The generator runs the same steps in every state, and the map is whatever those steps produce. Nobody looks at the result and fixes it.

The generator doesn’t know what a town, a county, a river, a highway or a neighborhood is. All it sees is how many people live in each census block and the block’s shape. So a line can run through a city, split a county or cross a bay. Bays are made of census blocks too.

“It looks wrong” usually means it doesn’t match a picture you already have, like the old district lines, the county map, or where you feel your area ends. People drew those pictures. Making the map match them would mean adding back the human choices this method leaves out.

Where odd edges come from

• Stair steps. The line follows census block edges and keeps every block whole, so a straight guide line becomes a ragged border.
• Notches and small bumps. The balancing pass moves single blocks across borders to even out the population, one block at a time.
• Across water. Water is census blocks like any other, so a district can join two shores, and an island link can join land no block reaches.
• Long or thin pieces. The shortest border wins each cut, and the people, not a neat outline, decide where that is. Sometimes it leaves a long piece.

Check it yourself

Every border traces back to a cut or a balancing move, and both can be replayed on the state’s map, starting with Colorado’s first cut. Anyone who reruns the generator gets the same map and the same fingerprint.

The rules themselves, shortest border and equal population, were chosen once and up front. They apply to every state alike and were fixed before any map existed. Nobody chose any single line.

5What is a census block?

A census block is the smallest area the U.S. Census Bureau counts people in. Blocks are bounded by things on the ground, such as streets, streams and railroad tracks, or by lines such as city and property limits. In a city a block is often an ordinary city block; in the countryside one can cover many square miles.

Every person in the country is counted in exactly one block, and the census publishes how many people live in each one. Some blocks have nobody in them. Blocks also cover lakes, bays and coastal water, out to the state’s legal boundary.

The maps are built from whole blocks. A block is never split between two districts, because the census only counts people per block: there is no count for part of one. That is why district borders follow block edges.

6How are ties settled?

Every tie has a fixed tiebreak, written down before any map was drawn. Nothing is left to chance or to a person. Where a tiebreak uses GEOID order, that is the census block identifier, a number the Census Bureau gives every block.

• Two borders the same length. Lengths are compared exactly as measured, so two borders tie only when they are exactly equal. When two different cuts tie, the one whose sides are nearer their fair shares of people is used, and if that is equal too, GEOID decides. No direction is preferred. Exact ties are rare.
• Where a cut stops. A cut adds up people block by block until one side has its share. If stopping just before a block and just after it land equally close to the share, both stopping points are kept as candidates and the border rules above choose between them.
• Blocks side by side. Blocks whose internal points are in exactly the same place are put in GEOID order.
• Which piece keeps its side. When a cut leaves a side in more than one piece, the piece with the most people stays, then the one holding the lower GEOID. The others are stray pieces and join the side around them.
• Which district balances first. If two districts are equally far from the ideal population, the one whose first block comes first in GEOID order goes first.
• Two equally good balancing moves. The move that leaves the shorter total border wins, then the block that comes first in GEOID order. If that block could go to two districts with the same result, it goes to the one whose first block comes first in GEOID order. District numbers never settle a tie.
• Two island links the same length. The link between the blocks that come first in GEOID order is added.

Each of these is spelled out under “The exact rule” in One cut, Stray pieces and Balancing.

7Does it use party, voting or race data?

No. Three facts about each census block go in: how many people the census counted there, where its edges are, and one point inside it, used to put blocks in order and to measure island links. Each chamber’s number of districts in each state goes in too. Nothing else does.

Party registration, election results, where officeholders or candidates live, the shapes of current or past district lines, and race, ethnicity, age or income never go in. For a State House or State Senate map, only the number of districts in the Census Bureau’s file is used. See What goes in.

8What does fair mean here?

Fair describes how a map is made, not who wins under it. A fair map is one nobody shaped. The lines come from one fixed rule that never sees party, votes or race, so no one can aim them at a result.

Equal is the one outcome the rule does promise. Every district in a chamber holds the same number of people, as close as whole census blocks allow, so each person’s vote counts the same.

Proportional means a party’s share of seats matches its share of votes. District lines can’t deliver that without gerrymandering. To hit a seat target, someone has to look at where each party’s voters live and draw around them, which is gerrymandering aimed at a different goal. Seats that follow votes need a different election system, such as filling seats from a statewide vote by each party’s ranked list of candidates. That is a change to how elections work, not to where the lines go.

Equitable usually means drawing lines to give a particular group a better chance. That requires seeing who lives where and choosing which groups count. That is gerrymandering too, however well meant, and stopping it is the whole point of the rule. It draws no district for or against any group.

So the promise is narrow on purpose: one rule everywhere, equal people in every district, and no one’s hand on any line.

9Why doesn’t it follow county or city lines?

County and city lines are never used to draw anything. The generator only knows people and block shapes, so a district border can split a county or a city when that gives the shortest border.

Counties are counted afterwards, for reporting only: the district list shows how many counties each district touches.

10Why aren’t the districts exactly equal?

They are as close as whole census blocks allow. People come whole, and a state’s population rarely divides evenly by its seats, so an even split already differs by one person. Missouri’s 6,154,913 people and 8 seats make an ideal of 769,364.125, so an even split puts each district at 769,364 or 769,365.

Each cut stops at the block that brings its sides closest to their shares. Then a balancing pass trades single blocks between neighboring districts, one at a time, as long as a trade brings the two districts closer to equal (or leaves them exactly as close and shortens the border) and keeps the district it leaves in one piece. It stops when no single-block trade helps. Blocks are never split, so a small difference can remain. See Balancing, and why it is needed, which lists the result in every state.

11Is this my district today?

No. These maps are drawn by the generator and are not the districts in use. To see the current lines, turn on “Compare with” on a state’s map: they are drawn as dashed lines, for comparison only. For the Federal House they come from the Census Bureau’s file of 119th Congress districts, so a state that adopted a new map after that file was made is not reflected. For the State House and State Senate they come from the Census Bureau’s 2025 state legislative district files (the sldl and sldu files), which also supply each chamber’s number of districts. Their shapes are never used to draw, and a state that adopted a new map after a file was made is not reflected.

12Why does a district cross water, or show dashed lines?

Census blocks cover lakes, bays and coastal water out to the state’s legal boundary, and a water block is a block like any other. So a district can join two shores across water. The map shows water paler so the land stands out, and shows the selected district’s water in full color.

Some land is not reached by any block, even across water, such as some islands. The generator joins it with an island link: the shortest link between internal points, added until every piece is connected. When a cut separates the two ends of a link, the link’s length counts in that cut’s border, like the water it crosses. When you select a district, its links show as dashed lines. See the island rule under “The exact rule” in Stray pieces and the re-count.

13Why does my state have only one district, and where is D.C.?

A Federal House map has one district for each House seat the state received in the 2020 apportionment. A State House or State Senate map has one district for each distinct district in the Census Bureau’s 2025 state legislative district files. A map with one district needs no cut, because the whole state is that district.

Nebraska has a single legislative chamber, so it has a State Senate map and no State House map.

Washington, D.C. and the U.S. territories are not drawn. They elect non-voting delegates to the House, and their local legislatures are not covered.

14Why don’t these maps follow my state’s redistricting laws?

Every map on this site, Federal House, State House and State Senate, is drawn by the same rule. We ignore requirements that individual states add on top, such as building senate districts out of whole house districts or keeping particular counties and towns together.

Those requirements were written by people with a stake in how the lines fall, and each one is another place where judgment can tilt a map. A single rule applied the same way everywhere leaves no such place, so we recommend that states adopt this method in place of their own rules.

We do keep one thing from each state: the number of districts. Each chamber gets the same number of districts it has today, and every district holds an equal share of the people.

15How can I check a map myself?

Every map has a fingerprint, a 64-character code worked out from the file that lists every block and its district. It is printed under “Check this map” on each map’s page. Change one block and the code changes completely.

The generator, this viewer and the published data are in the project’s GitHub repository. Run it on the same Census data and you get the same map and the same fingerprint, on any computer. See Same data, same map.

16What do the other terms mean?

The words this site uses, in the order you meet them.

Census block

The smallest area the Census Bureau counts people in. Every person is counted in exactly one. More under “What is a census block?” above.

GEOID

The identifier the Census Bureau gives every block: a 15-digit number made of its state, county, tract and block codes. Sorting by it gives one fixed order, which settles ties.

Internal point

One point inside each block, published by the Census Bureau. It is used to put blocks in order across a guide line and to measure island links.

Fair

Made by a rule nobody can aim. Fair describes how a map is drawn, not who wins under it.

Proportional

Seats shared out to match each party’s share of the vote. District lines can’t produce it without gerrymandering; it takes a different election system.

Chamber

One of the bodies a map is drawn for: the Federal House, the State House or the State Senate. Each is drawn separately, by the same rule.

Apportionment

How the 435 House seats are shared out among the states after each census. The Federal House maps use the 2020 apportionment.

Seat

The unit a map is divided into: one district. A Federal House map has one district for each House seat the state received. A State House or State Senate map has one district for each distinct district in the Census Bureau’s 2025 state legislative district files. Where a state elects more than one member from a district, the map still draws one district, because how many members a district elects is not modelled.

Cut

One split of a piece of the state into two sides, each with its share of the seats and the people. A state with [object HTMLElement] seats takes [object HTMLElement] minus 1 cuts.

Guide line

A straight line tried during a cut. It only decides which side each block joins; the real border then follows block edges.

Share

The number of people one side of a cut should hold: the piece’s people times that side’s seats, divided by the piece’s seats.

Border length

How long a cut’s real border is, measured along block edges. Of all the lines that work, the shortest border wins.

Stray piece

A block, or a group of blocks, cut off from the rest of its side by a guide line. It joins the side around it.

Re-count

After stray pieces move, the people are counted again and the line slides so each side still holds its share.

Connected

In one piece. Two blocks are connected when they share an edge; touching at a single corner does not count.

Island link

A link added between land that no block reaches, such as an island, and the rest of the state, so the state can still be cut. Its length, the distance between its two blocks’ internal points, counts toward a cut’s border when the cut’s sides meet across it. Shown as a dashed line on a selected district.

Ideal population

A state’s population divided by its number of seats: what each district would hold if people divided evenly.

Even split

The ideal rounded down or up to whole people. The map shows how far each district is from it.

Balancing

The last step: single blocks move between neighboring districts, one at a time, while that brings the districts closer to equal, or leaves them exactly as close and shortens the border. Balancing ranks people first, then border.

Fingerprint

A 64-character code worked out from the file that assigns every block to a district. The same map always gives the same code.

Current districts

The districts in use today, from the Census Bureau’s files: the Congress districts file for the Federal House, and the 2025 state legislative district files for the State House and State Senate. Shown as dashed lines for comparison only. Their shapes are never used to draw.