Drawing the lines of congressional and state legislative districts has been controversial since the early days of the republic. In the colonial era, governments used both land units and population as measures of apportionment. County-based systems of redistricting led to great differences in the number of people represented by each legislator. The U.S. Constitution incorporated both land-based (the Senate) and population-based (the House) representation. Most states entering the union used population-based representation in redistricting, but some used a combination of both. Malapportionment – unequal representation by population – was common as states limited the impact of population shifts to urban areas, preserving rural power in state houses.

Controversial too was the practice of gerrymandering – drawing political lines to favor incumbents or particular political parties. The term refers to Elbridge Gerry, the Democratic-Republican governor of Massachusetts who in 1812 sought to draw legislative district lines in his state in such a way as to ensure his party’s dominance of the state senate. The resulting map prompted an artist to add wings, claws and a beak to a Boston-area district. The press called the creature a “Gerrymander.”

Gerrymandering is still practiced today and takes many forms. Bipartisan gerrymandering occurs when political parties agree to draw lines favoring incumbents, thus discouraging newcomers and thwarting voters’ desire for change. Packing is a form of gerrymandering that occurs when lines are drawn to corral voters of one party substantially in one or more districts, thus diluting their power to affect the vote in other districts. Cracking is a form of gerrymandering that dilutes partisan voters’ strength by scattering them among several districts. These techniques have also been used to concentrate or dilute the voting power of minority groups.

By the early 1900s, population disparities among representational districts throughout the United States had become common. Yet courts initially were reluctant to insert themselves in the political machinations of redistricting. As late as 1946, in Colegrove v. Green, the United States Supreme Court declined to give relief in an Illinois case where one district had nine times more people than did another. By 1962, however, the U.S. Supreme Court had had a change of heart. In Baker v. Carr, the court intervened in a suit brought by urban residents who contested the make-up of the rural-controlled Tennessee Legislature, which had not been redistricted since 1901. The court held that complaints against malapportionment were “justiciable” and remanded the case to a lower court. The high court, however, did not specify what level of population disparity between districts could be constitutionally allowable.

But two years later, the U.S. Supreme Court established the “one-man, one-vote” rule, which had far-reaching impact on redistricting across the country. The court, in Wesberry v. Sanders, invoked the 14th Amendment’s equal protection clause, striking down Georgia’s congressional redistricting plan. The court said that “as nearly as is practicable, one man’s vote ought in a congressional election to be worth as much as another’s.”

In a second 1964 case, Reynolds v. Sims, the court held that both houses of a bicameral state legislature must be “based substantially on population.” The two high court decisions brought a flurry of lawsuits at the state level as reformers sought to correct years of malapportionment in state legislatures. By 1966, 46 of the 50 states had brought their apportionments into conformity with the standard of population equality.

While these court decisions helped address malapportionment, they proved not to be a cure-all for the problem of gerrymandering. Majority parties used the dictum for equal representation to justify bizarrely-shaped districts that preserved their status. In later years, the court began to allow some deviation in district population to preserve political boundaries and to recognize other factors important in representation, such as the cohesion of minority populations.

Redistricting is an iterative and highly contentious process. In many states partisan tensions and lawsuits accompany each redistricting cycle. One especially controversial redistricting example is the 2003 (mid-decade) congressional redistricting in Texas orchestrated by Tom DeLay specifically to maximize the number of Republicans in the Texas Congressional delegation. To prevent a quorum in the Legislature Texas Democrats fled across state lines, but ultimately the plan passed. The Supreme Court of the United States (in League of United Latin American Citizens v. Perry) upheld the new districts as being legal under the federal and Texas Constitutions.