Illinois's 12th Congressional District is represented by Mike Bost (Republican), who has held the seat since 2015. Bost has an overall VoteSee report card grade of B, voted in 98% of roll-call votes on bills this Congress, and votes with the Republican majority 94% of the time. The district includes O'Fallon, Carbondale, and Marion. It takes in all or part of 34 counties; the most populous parts are in St. Clair County and Williamson County. About 747,000 people live in the district, and the median household income is $68,540.
Current Representative
Mike Bost (Republican) has represented Illinois's 12th Congressional District since 2015.
VoteSee report card grade: B
Attendance in the 119th Congress: 98% of roll-call votes on bills
Incumbent Mike Bost is running for re-election. 2 candidates were on the Nov 3, 2026 ballot.
Mike Bost (Republican), incumbent: raised $1.6M, $845K cash on hand; VoteSee report card B; 98% attendance; votes with the Republican majority 94% of the time
Julie Fortier (Democratic): raised $162K, $34K cash on hand
Members of Congress who previously represented Illinois's 12th Congressional District. District lines are redrawn after each census, so earlier members may have represented a different area under this number.