1. In 1814, the first post office in what is now Illinois was established in Kaskaskia. Kaskaskia was the first state capital of Illinois and is located on an island in the Mississippi River.

2. On September 13, 1861, Camp Butler, a Union Army training camp located near Springfield, opened during the American Civil War. At its peak, the camp housed over 30,000 soldiers and played a crucial role in the Union's military efforts.

3. The first game at Wrigley Field in Chicago was played on September 13, 1914. The Chicago Cubs, who still play at the iconic stadium today, defeated the Cincinnati Reds 7-2.

4. On September 13, 1960, the first medical school in the state of Illinois, the University of Illinois College of Medicine, opened its doors. Today, the university's medical center is a leading research and patient care center in the country.

5. The Illinois State Fair, one of the oldest and largest state fairs in the United States, typically ends on September 13 or 14. The fair has been held annually since 1853 and attracts over 500,000 visitors each year.