1. On October 21, 1969, the Illinois State Police raided the Black Panther Party headquarters in Chicago, resulting in the deaths of two Black Panther members and the arrest of 21 others.
2. In 1975, Illinois Governor Dan Walker signed the abolished death penalty bill into law, making Illinois the first state to repeal the death penalty since it was reinstated by the Supreme Court in 1976.
3. On October 21, 1915, the world's first overhead electric train system made its debut in Chicago at the Illinois Central Railroad's electrified suburban service.
4. The University of Illinois at Urbana-Champaign was officially founded on October 21, 1867, with the signing of the "Charter of the University of Illinois," establishing the university as a land-grant institution.
5. On October 21, 1973, the Illinois Department of Transportation opened the new underground interchange connecting the Kennedy Expressway and the Dan Ryan Expressway in Chicago, known as the Circle Interchange. It was the first completely grade-separated interchange in Chicago.