1. In 1856, the "Sacking of Lawrence" occurred in Kansas, just a few miles from the Missouri border. This event was a violent raid by pro-slavery forces on the town of Lawrence, Kansas, which was largely inhabited by free-state advocates. Much of the pro-slavery sentiment that fueled the raid originated in Missouri.

2. On May 21, 1927, Charles Lindbergh made the first solo non-stop transatlantic flight, flying from Long Island, New York to Paris, France. Lindbergh was born in Detroit, Michigan, but lived much of his life in Missouri and attended college at the University of Wisconsin-Madison.

3. On May 21, 1830, the Indian Removal Act was signed into law by President Andrew Jackson. This piece of legislation paved the way for the forced relocation of tens of thousands of Native Americans from their ancestral lands east of the Mississippi River to destinations west of the river, including modern-day Oklahoma.

4. In 1972, the "Kelly Barnes Dam Collapse" occurred in Georgia, killing 39 people. The dam had been built by the Missouri-based consulting company, J.E. Greiner Co., and its failure resulted in a national discussion about dam safety and regulation.

5. On May 21, 1861, Union troops under the command of General Nathaniel Lyon occupied the Missouri state capital of Jefferson City. This act effectively put Missouri under Union control for much of the Civil War and helped to prevent the state from seceding and joining the Confederacy.