Gomillion v. Lightfoot
Voting districts within each state are subject to reassessment based upon federal census figures every ten years. In order to maintain an even population distribution among districts within each state, a reapportionment is done based upon population increases, decreases, and shifts. Redistricting may involve redrawing the boundaries of congressional districts in conjunction with the U.S. Constitution and Supreme Court cases with the intention that each individual's vote will be worth the same as another's.
Voting districts of equal population density assure that representatives to the U.S. House and state legislatures will be elected based upon an even apportionment of voters. Continual redistricting assures that voting precincts be divided equally based upon population figures, as much as possible. Care must be taken to insure that no boundaries are drawn that knowingly or unintentionally creates districts that discriminate against any group of voters.