1. Iowa became a state: On September 15, 1846, Iowa officially became a state, making it the 29th state in the United States.

2. Hawkeye State nickname: Since becoming a state, Iowa is famously known as the "Hawkeye State," after a character from James Fenimore Cooper's "The Last of the Mohicans." The state's flagship University of Iowa adopted the name for its mascot.

3. First Female Student Admitted to University of Iowa: Esther Allen Peterson became the first female student admitted to the University of Iowa Law School on this day in 1943. She went on to become a women's rights advocate and also served as the Director of the United States Women's Bureau.

4. Tri-State Tornado: On September 15, 1947, a massive tornado known as the Tri-State Tornado hit Iowa, Missouri, and Illinois. It was the deadliest tornado to hit the United States in history, causing 695 fatalities and injuring over 2,000 people.

5. National Bike Challenge: In 2014, the state of Iowa became the top state in the National Bike Challenge, with riders logging over 2 million miles during the six-month competition. The annual event encourages people to bike more and explore their communities on two wheels.