1. Earth Day was first celebrated on April 22, 1970, in Colorado and throughout the United States. The day was designated to raise awareness about environmental issues and promote sustainability.

2. In 1889, Colorado residents voted to approve a new state constitution, which established the framework for government and granted women the right to vote.

3. On April 22, 1914, a major coal mine explosion occurred in Ludlow, Colorado, which resulted in the deaths of 26 people, including 11 children. The tragedy led to widespread labor protests and strikes throughout the state.

4. In 1994, the Denver Nuggets set a new record for the largest deficit overcome to win an NBA playoff game. The team was down by 36 points to the Seattle SuperSonics but managed to come back and win 98-94.

5. The tamarisk plant, also known as salt cedar, was introduced to Colorado on April 22, 1877. The plant, which was originally brought in to help stabilize soil and protect against erosion, has since become a major invasive species in the state's riparian areas.