The population in Illinois has grown over the last decade, but it has grown at a much slower rate than southern and western states like Nevada, Texas and California.
The fight over which one will disappear is going to start early next year.
Nationally, the loss of a congressional seat in a state like Illinois with a large, mostly democratic urban area like Chicago would hurt the Democrats and help Republicans. That's because the population growth has shifted to more traditional GOP states in the South and Southwest.
However, in Illinois, Democrats are still in power, and they can control the process for redrawing the district maps that will eliminate one congressional seat.
"The Democrats control the redistricting process. Governor Quinn has indicated that he wants to have a competitive map, but I don't believe that's Speaker Madigan's wish," said Illinois Republican Chair Pat Brady.
Kwame Raoul will lead the redistricting process in State Senate in Springfield. He says Democrats and Republicans are just two of the many groups with a vested interest in the process; minority groups are also among those who want fair representation.
"It shouldn't be just reduced to a notion of partisan battle," said Raoul. "There are various communities fighting for all sorts of different interests in the redistricting process."
There are 435 seats in Congress and Illinois will have 18 of them, four fewer seats than Illinois had 20 years ago.
Illinois is one of ten states losing a Congressional seat. While its population has increase 3 percent between censuses, it did not increase enough to avoid losing a seat.
The census pegged the overall U.S. population at 308,745,538.
As the state's influence in Washington is diminished, the fight over who gets those seats intensifies, with Democrats promising fairness and Republicans saying they are skeptical.
"People are looking at the fact Democrats have control of both chambers, as well as Democratic governor, but redistricting is a bit more complex than that, and so you can have interparty fighting as well," said Raoul.
"It's all up to the Democrats right now, and I appeal to their better good that they make a competitive map, but I don't think they will," said Brady.
The State Senate has already passed an Illinois voting rights act. It goes to the House for a vote early next year.
The act is written to insure that minority groups' voices are heard in the redistricting process. Among other things, it calls for four public hearings around the state before lawmakers approve a new map of congressional districts.
The census is also expected to show large gains in the Latino population, which could translate to increased influence and representation at nearly every level of government.
"All the way from the courthouse to the White House, it does have an impact, and Latinos will have an increasingly growing impact," said Juan Andrade, Jr., president of the U.S. Hispanic Leadership Institute.
The Voting Rights Act would call on lawmakers to hold at least four meetings around the state to solicit input from citizens on redistricting. If approved, the first of those meetings would be held in early 2011.