The tournament is open to professionals and amateurs with a handicap of 10 or less who reside within the state of Illinois.
In 2015, for the first time in the history of the Illinois Open, the Illinois PGA changed the format of the event having it contested at two facilities for the first and second rounds.
The final championship field size after qualifying events increased from 156 to 258 players.
Qualifying events conducted throughout the month of June finalize the championship field to the top 258 players.
The modern incarnation of the Illinois Open dates back to 1950.