1. In 1837, the first train arrives in Chicago, traveling from the east coast. The train was the Galena and Chicago Union Railroad, which helped spur the city's growth as a transportation hub and one of the largest cities in the United States.

2. In 1865, William Booth, founder of the Salvation Army, holds the organization's first meeting in the United States in a tent in Chicago. The meeting marks the beginning of the Salvation Army's work in the United States, which has since become one of the country's largest charitable organizations.

3. In 1921, the first radio broadcast of a Major League Baseball game is transmitted from Chicago. The game was between the Chicago Cubs and the Pittsburgh Pirates, and was broadcast on station WGN, which later became one of the largest radio and television stations in the Midwest.

4. In 1943, the first nuclear reactor designed for peaceful purposes begins operation at the University of Chicago. The reactor, known as Chicago Pile-1, was a crucial development in the development of nuclear power and helped pave the way for advances in medical imaging, research, and energy production.

5. In 2017, the Illinois state legislature passes a bill making Illinois the first state to require insurance companies to cover the cost of EpiPens for children with severe allergies. The law was designed to ensure that families in Illinois have access to lifesaving medications, regardless of their ability to pay.