In 1812, the Boston Gazette published an editorial cartoon in response to a redistricting plan signed into law by Massachusetts Governor Elbridge Gerry. The cartoon depicted a portion of Essex County in Massachusetts seemingly haphazardly drawn into a district that would benefit Gerry's Democratic-Republic party. The newly drawn district resembled a salamander, and the artist titled his cartoon "the Gerry-mander." The label stuck and gerrymandering entered the American political vocabulary.
Gerrymandering, the redrawing of electoral district boundaries to favor a particular political group, has its roots in the US Constitution. Article I Section 2 states that members of the US House of Representatives are to be apportioned among the states based on their population as determined every 10 years by census, at a ratio of one Representative for every 30,000 persons. The federal government apportions [PDF] districts among the states based on populations, and then the state legislatures draw the district lines. The Apportionment Act of 1842 established the basic standard that the states divide their territory into individual districts for each representative. In Wesberry v. Sanders, the US Supreme Court held that in the context of apportionment "as nearly as is practicable one man's vote in a congressional election is to be worth as much as another's" and districts should contain a near-equal population.
Over time there have been three recognized [PDF] types of gerrymandering. State legislatures redraw lines in order to favor one political party over another through "partisan gerrymandering," to limit the influence of minority populations on elections through "racial gerrymandering," or to favor incumbent representatives through "incumbent gerrymandering." Congress included sections in the Voting Rights Act of 1965 to diminish the effects of racial gerrymandering. Section 2 of the law prohibits redistricting plans that discriminate on the basis of race. In June 2013, however, the Supreme Court struck down Section 4 of the Act, and thus muted Section 5's requirement that certain states redistricting plans be subject to review by the US Attorney General or to lawsuits in federal District Courts for a determination that the plan does not discriminate.
The court explored a variety of gerrymandering issues in the context of North Carolina's 12th Congressional District. In Shaw v. Reno, the court held that state citizens had a valid claim under the Equal Protection Clause when they alleged that the state deliberately segregated voters into districts based on race and remanded the issue to the District Court. In Shaw v. Hunt, the Court examined the District Court's finding that North Carolina engaged in racial discrimination when it redrew the 12th District and held that the redistricting was invalid because it was not narrowly tailored to serve a compelling interest. Finally, in Hunt v. Cromartie, the court stated that a "jurisdiction may engage in constitutional political gerrymandering, even if it so happens that the most loyal Democrats happen to be black Democrats and even if the State were conscious of that fact."