1. World's First Skyscraper Built: On September 24, 1885, the world's first skyscraper, the Home Insurance Building, was completed in Chicago. This building was considered a technological marvel of its time, soaring 10 stories and used a structural system that contained a steel skeleton to support the weight of the building’s floors.

2. International Chicago Underground Film Festival: The International Chicago Underground Film Festival, an annual film festival that showcases underground and independent films, started on September 24, 1993. It's a four-day event that takes place at the Logan Theatre.

3. Illinois Constitution Signed: On September 24, 1818, when Illinois became a state, the Illinois Constitution was signed. Its creation paved the way for Illinois to become an equal member of the United States, allowing its citizens the same rights and protections afforded to those in other states.

4. Giant Oarfish Caught: In 2013, a 18-feet-long oarfish was found dead on the shore of Catalina Island. The oarfish was caught by local fisherman in the months of September, making its discovery one of the five interesting facts about Illinois history on September 24.

5. State Fair Started: On September 24, 1853, the first Illinois State Fair was held in Springfield. The event was held to showcase the state's agricultural products, but today has grown to include carnival rides, live music, and a variety of competitions, bringing millions of visitors to the state.