All Intensive Purposes

I have an idea about gerrymandering, but first some background from Wikipedia (internal links and a fair amount of text omitted):

Gerrymandering is a controversial form of redistricting in which electoral district or constituency boundaries are manipulated for electoral advantage, usually of incumbents or a specific political party, mainly in two party first past the post systems. Gerrymandering is most effective in electoral systems with districts that elect a single representative, which include first-past-the-post, or single-member district and plurality, electoral systems, and majority run-off, or single-member district and majority, electoral systems.

One form of gerrymandering occurs when the boundaries of a constituency are changed in order to eliminate some area with a high concentration of people who vote in a similar way (e.g., for a certain political party). Another form occurs when an area with a high concentration of similar voters is split among several districts, ensuring that the party has a small majority in several districts rather than a large majority in one. A converse method is to draw boundaries so that a group opposing those manipulating the boundaries are concentrated in as few areas as possible, so as to minimise their representation and influence. Often, such gerrymandering is held to redress a long-overlooked imbalance, as when creating a black majority district.

In the United States, gerrymandering has been used to cut minority populations in half to keep all minorities in the minority, in as many districts as possible. This led to a major civil rights conflict; gerrymandering for the purpose of reducing the political influence of a racial or ethnic minority group is illegal in the United States under the Voting Rights Act of 1965, but redistricting for political gain is constitutional.

Certainly there is an ample history of gerrymandering in this country:

The carving of territories into US states was also subject to gerrymandering, where before the American Civil War states were admitted on a formula of "one free state for each slave state". This nearly prevented Maine from seceding from Massachusetts until the Missouri Compromise was agreed upon, and it was decided that Texas and California would both enter as single - but large - states. During the late 19th century, the territories of the Rocky Mountains were split up into relatively small states to help the Republican Party maintain control of the White House — each new state brought in three electoral votes (Compare a map of the United States in 1860 with a map from 1870).

In recent years, the Supreme Court has addressed gerrymandering in the context of the Equal Protection Clause:

As for state-internal gerrymandering, there have been attempts to create "majority minority" districts, also called "affirmative gerrymandering" or "racial gerrymandering", to ensure higher ethnic minority representation in government. However, gerrymandering based solely on race has been ruled unconstitutional by the US Supreme Court, under the Fourteenth Amendment first by Shaw v. Reno (1993) and by subsequent cases, including Miller v. Johnson (1995) and Hunt v. Cromartie (1999).

The possibility of gerrymandering makes the process of redistricting extremely politically contentious within the United States. Under U.S. law, districts for members of the House of Representatives are redrawn every ten years following each census and it is common practice for state legislative boundaries to be redrawn at the same time. Battles over contentious redistricting take place within state legislatures, which are responsible for creating the electoral maps in most states, as well as federal courts. Sometimes this process creates strange bedfellows; in some states, Republicans have cut deals with African American Democratic state legislators to create majority black districts. These districts essentially ensure the election of an African American Congressman, but due to voting patterns, end up concentrating the Democratic vote in such a way that surrounding districts are more likely to vote Republican.

While race has been the central focus of the Supreme Court's recent decisions, a less obvious factor driving the issue's prominence is techological change -- the advent of computer technology.

The introduction of computers has made redistricting a more precise science, but the incentives for certain groups to create maps that increase their delegation in Congress remain. Many political analysts have argued that the United States House of Representatives has been gerrymandered to the point that there are now very few contested seats, and have also argued that this has a number of detrimental effects, among which is that the lack of contested seats makes it unnecessary for candidates to attract middle voters and to compromise across party lines.

Thanks to gerrymandering, you get congressional districts like Georgia's Seventh, New York's Twelfth, and Illinois's Fourth:

(Thanks, National Atlas!)