Data & Methodology

District boundaries & maps

The game and the district profiles use the congressional district boundaries currently in effect — the plans used to elect the current U.S. House. District geometry is built from official block-assignment files, which specify exactly which Census blocks belong to each district, paired with U.S. Census Bureau TIGER/Line and cartographic boundary geography. When a state adopts a new map (through litigation or mid-decade redistricting), the affected districts are rebuilt from the new plan.

The interactive maps are rendered from simplified versions of this geometry so pages load quickly; zooming into a state swaps in higher-detail boundaries. Land area figures come from the same geometry, so the acreage, density, and compactness figures on a profile all describe the same shape.

Demographics

Population and demographic figures come from the U.S. Census Bureau's American Community Survey (ACS) 5-year estimates, retrieved directly from the Census Bureau API and aggregated from census tracts to districts using the block-assignment files above. That tract-level aggregation is what lets the profiles report demographics for current district lines even where they differ from the boundaries the Census Bureau publishes district tables for.

A note on categories: "White" refers to non-Hispanic White alone; "Hispanic" includes people of any race; "Black" and "Asian" refer to people identifying with those races alone. Percentages may not sum to 100 because of rounding and smaller groups collected under "Other." As with all ACS estimates, figures are survey-based and carry margins of error — treat small differences between districts as approximate.

Source: U.S. Census Bureau, American Community Survey 5-year estimates; 2020 Decennial Census (P.L. 94-171) for total population baselines.

Election results

2024 presidential results by congressional district (Harris vs. Trump) come from The Downballot's district-level calculations. 2020 presidential results are computed from precinct-level election returns reallocated to the current district boundaries, so both elections describe the same lines even where districts have since been redrawn. Margins are reported as two-party leans — for example, D+3 means the Democratic candidate ran three points ahead of the Republican in that district.

Sources: The Downballot (2024); precinct-level returns aggregated to current districts (2020).

Representatives

The current U.S. House member for each district comes from official House sources (house.gov) and is updated periodically. When a seat is vacant — after a resignation or death, before a special election — the profile says so rather than listing a former member. Party labels are those the member serves under in the House.

Source: Official listings at house.gov.

Compactness & shape statistics

Each profile reports a Polsby-Popper compactness score: 4πA / P², where A is the district's area and P its perimeter. The score runs from 0 to 1 — a perfect circle scores 1.0, and the more contorted a district's boundary, the closer it falls to 0. It's one of the standard measures courts and scholars use when evaluating whether a district's shape is "regular," though no single number can prove or disprove a gerrymander on its own.

All geometric calculations — area, perimeter, compactness, and which districts border which — are done in an equal-area map projection (the US National Atlas projection) so that scores are comparable across every state, including Alaska and Hawaii. One caveat inherent to the measure: districts whose edges follow naturally jagged features like coastlines score lower than their appearance on a map might suggest.

Accuracy & corrections

All of this data is assembled for education, not as an official record — for authoritative figures, consult the underlying sources directly. If you spot something that looks wrong on a district profile, please email jcervas@andrew.cmu.edu and we'll investigate and correct it.