Segregation Lab: Three American Metros
Interactive geography lab
Draw the Line
The voters stay where they are. The population stays equal. Only the boundaries move, and political power moves with them.
One state, many possible maps
Mapporia has 640,000 people in 64 equal-population blocks. It needs four districts of exactly 160,000 people. Begin with a preset, then swap blocks to change the boundaries without changing district population.
This is a teaching simulation, not a real electoral map. Each block contains 10,000 people. Vote and community patterns are synthetic but geographically plausible.
Map layer
Start with a plan
Swap equal-population blocks
A fair map has more than one ruler
Equal population is necessary, but it does not settle compactness, communities, competition, partisan outcomes, or minority electoral opportunity. Read the same map through several measures.
District results
| District | Blue vote | Community | Shape | Result |
|---|
Map scorecard
No single score proves that a map is fair. Compactness can preserve a community or cut through it. Competitiveness can make elections responsive or divide a coherent voting community. A measure reveals one value by temporarily hiding others.
Packing
Concentrate the other side's voters into a small number of districts they win overwhelmingly.
Cracking
Split the other side's voters among several districts so they rarely form a winning majority.
Self-packing
Voters are not distributed randomly. Urban concentration can produce lopsided districts even without a line-drawer's partisan intent.
Legal does not mean neutral
Redistricting rules form a narrow passage. Maps must equalize population and obey federal voting-rights protections, while states add their own rules. Yet federal courts generally do not decide claims of purely partisan gerrymandering.
Equal population
Congressional districts must be nearly equal in population. The Census Bureau supplies block-level population and voting-age data used in the process.
Race and voting power
Section 2 of the Voting Rights Act remains central, but the Supreme Court's 2026 Callais decision tightened the constitutional limits on race-predominant districting.
Partisan claims
In Rucho v. Common Cause (2019), the Supreme Court held that partisan-gerrymandering claims present political questions beyond federal courts.
Traditional criteria
States may require contiguity, compactness, respect for political subdivisions, or preservation of communities of interest.
Who draws?
Legislatures, commissions, and courts do not bring the same incentives or public procedures to the same geographic task.
Notice race, but how?
Mapmakers cannot ignore racial discrimination, but using race as the predominant factor can itself trigger strict constitutional scrutiny.
Classify the claim
A map has equal population, but one district is split into two disconnected islands.
Three states, three political geographies
The map is only the visible residue of a process. Compare Minnesota, Illinois, and North Carolina to see how institutions and timing become part of the geography of representation.
Minnesota: divided government, judicial map
Your commission cannot maximize everything
You have six political points. Select priorities for the next map. The activity will assemble a defensible public explanation and name the principle your commission sacrificed.
No decision yet
Select priorities costing no more than six points, then issue the commission decision.
Sources and model limits
The synthetic map uses equal-population blocks and simplified partisan and community indicators. Its minority-opportunity measure is an instructional signal, not a legal test. Actual Section 2 analysis depends on detailed facts, voting patterns, history, and current law.
U.S. Census Bureau, 2020 Census Redistricting Data; U.S. Department of Justice, Redistricting Information; U.S. Supreme Court, Rucho v. Common Cause (2019) and Louisiana v. Callais (2026).
U.S. Census Bureau, 2020 congressional apportionment; Minnesota Judicial Branch, 2021 Special Redistricting Panel final plans; North Carolina General Assembly, Legislative and Congressional Redistricting; Illinois General Assembly, Illinois Congressional Redistricting Act of 2021.
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