1. Missouri became a state: March 31, 1821 is a significant date in Missouri history as it marked the day that Missouri officially became a state of the United States. The territory of Missouri was officially granted statehood after years of fighting over the issue of slavery.

2. Truman Library dedicated: On March 31, 1957, the Harry S. Truman Library and Museum, located in Independence, Missouri, was dedicated. The library was built to honor Truman, who served as the 33rd President of the United States from 1945 to 1953.

3. Tornado outbreak: On March 31, 1973, a massive tornado outbreak hit Missouri, causing widespread damage and devastation. The tornadoes, which hit communities across the state, resulted in 48 fatalities and over a thousand injuries.

4. Arch construction completed: March 31, 1965, marked the day that construction was completed on the iconic Gateway Arch in St. Louis, Missouri. The arch, which stands at 630 feet tall, is the tallest man-made monument in the United States.

5. Missouri's first licensed female physician: On March 31, 1870, Dr. Julia Steele became the first licensed female physician in the state of Missouri. Dr. Steele overcame tremendous gender-based discrimination to become a physician and paved the way for other women to pursue careers in medicine.