1. On February 15, 1859, the first gold was discovered in Colorado by a group of prospectors near the confluence of the South Platte River and Cherry Creek. This event led to the Pike's Peak Gold Rush and the subsequent settlement of Colorado.

2. The Ku Klux Klan held their first public meeting in Colorado on February 15, 1923, in Denver's city park. The Klan had a significant presence in Colorado during the 1920s and 30s, and their influence was felt in politics and social issues.

3. February 15, 1952, was a significant day in Colorado aviation history, as a United Airlines DC-6B crashed into the Flatirons near Boulder, killing all 50 people on board. This tragedy highlighted the need for improved air traffic control and safety regulations.

4. In Colorado's political history, February 15, 2012, was a significant day as the state's legislature passed a bill legalizing civil unions for same-sex couples. Colorado was one of the first states in the nation to enact such a law by a legislative vote rather than court order or voter referendum.

5. On February 15, 2018, a wildfire broke out near Durango, Colorado, that eventually grew to become the sixth-largest in state history. The 416 Fire burned over 54,000 acres and forced the evacuation of some 2,000 homes before being brought under control in July 2018. The cause of the fire is believed to have been human-caused.