The Congressional District map above in suburban Chicago is an example of Gerrymandering. Gerrymandering is the process of designing Congressional or State Districts to optimize your parties chances.  In most states the Legislature draws the map, so the party in power following the annual census gets to decide the districts for the next ten years. The party in power draws the districts to get safe seats for their people, usually trying for about a small majority of the voters in the District in their party, while drawing districts for the other party with as many voters from the other party as possible.

The map above is an excellent example of gerrymandering.  This was done in part to create a Democratic District, but also to create a Hispanic District.

One of the problems of gerrymandering is that it creates safe one party districts.  The Congressmen enjoy this since it makes reelection easier, but it polarizes the country, since the primary is the most important election.  The people who vote in the primaries tend to be the most passionate and extreme.  The Congressman must vote to satisfy the extreme wing of his party, and is punished if he compromises.

"The 4th Congressional District of Illinois includes part of Cook County, and has been represented by Democrat Luis Gutierrez since January 1993.

It was featured by The Economist as one of the most strangely drawn and gerrymandered congressional districts in the country[2] and has been nicknamed "earmuffs" due to its shape.[3] It was created to contain two majority Hispanic parts of Chicago.

This district covers two strips running east-west across the city of Chicago, Illinois on the west side continuing into smaller portion of some suburbanareas in Cook County, surrounding Illinois' 7th congressional district. The northern portion is largely Puerto Rican, while the southern portion is heavily Mexican. The two sections are on opposite sides of the city and are only connected by a piece of Interstate 294 to the west; the highway is in the district while the surrounding areas are not."