The conference participated in athletics and activities in the Illinois High School Association.

The conference comprised 28 small private schools, with enrollments between 50 and 400 students, in Bureau, DuPage, Kane, Lake, LaSalle, McHenry, Will, and Winnebago counties.

Chicago Central YMCA withdrew in 1939, leaving the league with a total of 10 teams as the 1940 school year commenced.

In 1955, Walther Lutheran High School (Melrose Park) joined the league.

In 1987, Providence Catholic High School left while in 1995, St. Gregory and Peru St. Bede joined.