1. In 1835, the city of Chicago was officially incorporated as a city. This marked a turning point in the city's growth, and it quickly became a major industrial and transportation center.

2. On September 15, 1858, Abraham Lincoln delivered his famous "House Divided" speech in Springfield, Illinois. This speech is widely considered to be one of the most important speeches in American history, as it marked the beginning of Lincoln's campaign for the Presidency and helped to define the issues that would ultimately lead to the American Civil War.

3. In 1893, the World's Columbian Exposition opened in Chicago. This historic event brought millions of visitors to Chicago and showcased some of the greatest technological and cultural achievements of the time.

4. On September 15, 1912, the state of Illinois adopted its first official state flag. The design features the state seal on a white background, and has remained largely unchanged to this day.

5. In 1963, a bomb exploded at the 16th Street Baptist Church in Birmingham, Alabama, killing four young girls. This heartbreaking event sparked a wave of civil rights protests across the country, including in Chicago, where demonstrators marched through the streets in support of the cause.