1. Indiana becomes a state: On May 15, 1816, Indiana became the 19th state of the United States. The state was carved out of the Northwest Territory, which had been ceded to the federal government at the end of the Revolutionary War.

2. Indianapolis 500: The first Indianapolis 500 was held on May 30, 1911, but the event was originally scheduled for May 15, which was later pushed back due to inclement weather. The race has become a mainstay of Indiana's culture, attracting fans from all over the world.

3. Purdue University established: On May 6, 1869, Indiana Governor Conrad Baker signed a bill establishing what would become Purdue University. The institution has since become one of the state's major centers of higher education.

4. Indiana State Fairgrounds Coliseum opens: The Indiana State Fairgrounds Coliseum, which has hosted a variety of events over the years including concerts, sports games, and political rallies, officially opened on May 15, 1939.

5. Monument Circle constructed: One of Indianapolis' most iconic landmarks, Monument Circle, was completed on May 22, 1901. The structure features a statue of Governor Oliver P. Morton and has become one of the city's most recognizable symbols.