The 18th congressional district of Illinois covered central and western Illinois, including all of Jacksonville and Quincy and parts of Bloomington, Peoria, and Springfield. It covered much of the territory represented by Abraham Lincoln during his single term in the House.
It was last represented by Republican Darin LaHood, who took office in September 2015 following a special election.
Republican Aaron Schock previously represented the district from January 2009 until his resignation in March 2015. Darin LaHood is the son of Schock's predecessor, Ray LaHood, and was reelected in 2016, 2018, and 2020.
From 1949 to 2015, the district was always represented by an attendee or graduate of Bradley University. Due to reapportionment after the 2020 U.S. census, the 18th district was eliminated ahead of the 2022 elections.
The district covered parts of McLean, Peoria, Sangamon, Stark and Tazewell counties, and all of Adams, Brown, Cass, Hancock, Logan, Marshall, Mason, McDonough, Menard, Morgan, Pike, Schuyler, Scott and Woodford counties, as of the 2011 redistricting which followed the 2010 census. All or parts of Bloomington, Chatham, Jacksonville, Lincoln, Macomb, Morton, Normal, Peoria, Quincy and Springfield were included. The representatives for these districts were elected in the 2012 primary and general elections, and the boundaries became effective on January 5, 2013.
Due to Illinois losing population in the 2020 United States census, the district was eliminated in January 2023.
Ray LaHood decided not to seek re-election in 2008 and was chosen by Barack Obama to serve as U.S. Secretary of Transportation. Illinois State Representative Aaron Schock of Peoria won the seat for the Republicans in the November 4, 2008 election. His main opponent was Democrat Colleen Callahan, of Kickapoo, a radio and television broadcaster. Green Party candidate and educator Sheldon Schafer, of Peoria, was in a distant third place on the ballot.