1. In 1858, gold was discovered in Colorado, leading to the Pike's Peak Gold Rush. This event helped Colorado become a state.

2. June 21, 1972, marked the start of the Buffalo Creek Disaster. A dam had burst, causing a massive flood that destroyed everything in its path, killing 1 person and causing over $100 million in damages.

3. In 1937, the Colorado River Compact was signed, dividing the waters of the Colorado River between the seven western states, including Colorado.

4. On June 21, 1915, Denver hosted the 59th annual National Education Association convention. The theme was "A Nation's Duty to Its Children," which aimed to promote education reform throughout the country.

5. The first-ever Colorado State Fair was held in Pueblo on June 21, 1872. The fair has since become an annual tradition, where people come from all over to enjoy the food, music, and agricultural exhibits.