An Act of the Twenty-sixth General Assembly of Illinois, approved March 9, 1869, created Southern Illinois Normal College, the second state-supported normal school in Illinois. Carbondale held the ceremony of cornerstone laying, May 17, 1870. The first historic session of Southern Illinois Normal University was a summer institute, with a first faculty of eight members and an enrollment of 53 students. It was renamed Southern Illinois University in 1947.
The university continued primarily as a teacher's college until Delyte W. Morris took office as president of the university in 1948. Morris was SIU's longest-serving president (1948–1970). During his presidency, Morris transformed SIU, adding Colleges of Law, Medicine and Dentistry. Southern Illinois University grew rapidly in size from 3,500 to over 24,800 students between 1950 and 1991.
In 1957, a second campus of SIU was established at Edwardsville. This school, now known as Southern Illinois University Edwardsville, is an independent university within the SIU system.
SIU offered the first program to provide support to students with specific learning disabilities at a college level. "Project Achieve" was founded at SIU by Barbara Cordoni Kupiec in 1978. She pursued a career in the field initially to help her own children and has left behind a legacy that has assisted several thousand other students in earning their degrees. In 1983, Project Achieve became the Clinical Center Achieve program when SIUC decided to institutionalize the program, making it a permanent part of the university's structure.