1. On December 11, 1875, Colorado became the first state to allow women to vote in state elections, making it a pioneer in women's suffrage.

2. On December 11, 1958, the US Air Force Academy was officially dedicated in Colorado Springs. The academy has trained countless military leaders and pilots, and its stunning modernist architecture has become a notable landmark.

3. December 11, 1903 saw the first successful snowmobile prototype tested in Hot Sulphur Springs, Colorado. The invention would revolutionize winter transportation and popularize snow sports in the state.

4. In 1978, a catastrophic plane crash occurred on December 11, when a United Airlines flight crashed into a frozen mountain in the Colorado Rockies, killing all 182 people on board in one of the deadliest aviation disasters in US history.

5. On December 11, 2015, Colorado became the first state to legalize the use of recreational marijuana. The landmark decision has had significant societal and economic impacts, with the state generating billions of dollars in revenue from cannabis-related businesses.