The Illinois Republican Party is the affiliate of the Republican Party in the U.S. state of Illinois founded on May 29, 1856. It is run by the Illinois Republican State Central Committee, which consists of 18 members, one representing each of the state's congressional districts. Once the dominant party in Illinois, the state GOP has become a minority party within the last few decades, holding little power in the state. The current chairman is Don Tracy, who has served since 2021.

Decatur is the largest city in and the county seat of Macon County, Illinois, United States. The city was founded in 1829 and is situated along the Sangamon River and Lake Decatur in Central Illinois. As of the 2020 census, it had a population of 70,522. It is the seventeenth-most populous city in Illinois. Decatur has an economy based on industrial and agricultural commodity processing and production. The city is home to Millikin University and Richland Community College.