Kirkpatrick v. Preisler

Background

Missouri’s Legislature adopted a new congressional map in 1967. Voters challenged the map in federal court, which found large population differences among the State’s ten districts and ruled the plan unconstitutional under the principle that each person’s vote should be worth roughly the same amount. The plan’s districts ranged about 25,802 people from largest to smallest (about +3.13% to -2.84% from the ideal), and the District Court found the Legislature had used inaccurate data and rejected plans that would have been closer to equality.

Reasoning

The central question was how close states must come to equal population when drawing congressional districts. The Court said states must make a good-faith effort to achieve near-equal populations and must justify any remaining differences, no matter how small. The Court rejected a fixed “de minimis” percentage that would automatically make small variances acceptable. It also rejected common justifications Missouri offered—protecting local economic or social interests, preserving county lines or compact shapes, relying on political compromise, projecting population without solid documentation, or claiming many nonvoters live in a district—because Missouri failed to document or apply these reasons systematically.

Real world impact

States drawing congressional maps must aim for near-equal district populations using reliable data and must explain any deviations. Maps with unexplained or poorly documented population variances can be struck down even if percentage differences seem small. This decision strengthens the requirement that numerical equality, not political convenience or pleasing maps, govern congressional apportionment.

Dissents or concurrances

A concurring Justice agreed the Missouri plan was invalid on this record but warned the Court’s strict demand for near‑perfect equality risks ignoring census imprecision and practical realities when small disparities occur.