1. In 1859, the first gold rush of Colorado began when a group of prospectors discovered gold in the South Platte River.

2. On May 11, 1907, the first Denver Auto Show opened to the public, featuring 41 different makes and models of cars.

3. In 1975, the Colorado Rockies began their first season as a Major League Baseball team. They played their inaugural game on May 11 against the New York Mets.

4. On May 11, 2017, Colorado Governor John Hickenlooper signed a bill legalizing the sale and consumption of marijuana in public places, making Colorado the first state to allow public marijuana use.

5. In 1917, the deadliest train wreck in Colorado history occurred near Trinidad, killing 121 people and injuring over 100 others. The tragedy took place on May 11, and was caused by a malfunctioning train signal.