1. Winter Solstice: December 21 marks the winter solstice in Colorado, which is the shortest day and longest night of the year in terms of sunlight. The winter solstice has been celebrated by many cultures throughout history and is often associated with the rebirth of the sun.

2. First Ski Resort: On December 21, 1936, the first ski resort in Colorado opened at Berthoud Pass. The resort featured a single rope tow and was an instant success, attracting skiers from all over the state.

3. Colorado's Statehood: Colorado was admitted to the Union as the 38th state on December 21, 1876. This followed a long struggle for statehood, as Colorado's application had been repeatedly rejected due to its relatively small population.

4. Blizzard of 2006: On December 21, 2006, a blizzard swept through Colorado, dropping over two feet of snow in some areas and causing widespread transportation disruptions. The storm was one of the most severe to hit the state in recent history.

5. Birth of John Denver: John Denver, the famous singer and songwriter, was born in Roswell, New Mexico on December 31, 1943. Though he did not hail specifically from Colorado, he spent much of his career in the state, and his music has become synonymous with the Colorado lifestyle.