Eagle-eyed blog readers will recognize the 5th least compact U.S. House district, Illinois’s Fourth Congressional District, from our earlier post, or perhaps from an article in The Economist called “How to Rig an Election” or the slideshow accompanying a Slate piece on the use of mathematical algorithms in redistricting. What is it about this Chicago district that attracts so much attention and how did it come to look this way?

Illinois's 4th Congressional District: The 5th least compact U.S. House District

Unlike some of the entries in our Top Ten list, IL-04 is an inland district whose shape has no apparent relationship to physical geography. The two major portions of the district are connected by a thin, C-shaped thread that is just one block wide in many places, running along railroad tracks and tracing Interstate 294 to the west. The district’s boundaries were drawn in relation to human geography, capturing two majority Hispanic communities—a largely Puerto Rican one to the north and a largely Mexican one to the south—and almost surrounding the majority African-American IL-07, which extends to the east.

The post-2000 Illinois Congressional redistricting plan was the subject of multiple lawsuits, some of which charged that it failed to meet the compactness requirements of the state constitution. The district is yet another illustration of the tensions inherent in the redistricting process, between the value of compact districts and the Voting Rights Act requirement that ethnic minorities have sufficient opportunity to elect candidates of their choice.

The case of IL-04 also represents the challenge (likely to grow as the country’s Latino population increases) of drawing districts that afford both African-American and Latino communities the chance at elected representation, particularly in urban areas where these populations often live side by side but may be geographically dispersed due to historical patterns of urban development.

We suspect that 2011 will bring many more lawsuits challenging the spatial interpretation of the Constitution and the Voting Rights Act—not to mention political self-interest—that legislative district boundaries represent.