1. In 1857, the University of Michigan admitted its first female student, Madelon Louisa Stockwell, marking the beginning of coeducation at the university.

2. On October 20, 1881, the Grand Rapids Furniture Association was formed, which brought together furniture manufacturers in the Grand Rapids area and helped establish the city as a major hub for furniture production.

3. The Detroit Pistons played their first regular-season NBA game on October 20, 1957, against the Minneapolis Lakers. Although they lost the game, it marked the beginning of professional basketball in Detroit.

4. On October 20, 1973, the Detroit Tigers won the American League pennant by beating the Oakland Athletics in the seventh and deciding game of the ALCS. The team went on to lose the World Series to the New York Mets.

5. In 2018, a meteorite that crashed into Michigan's Hamburg Township on January 16 was found to contain organic compounds, making it one of the most important meteorites ever discovered. The discovery was announced on October 20 of that year.