1. Statehood Day: December 21st marks Wyoming's Statehood Day! In 1890, Wyoming became the 44th state in the United States.

2. Women's Suffrage: Wyoming was the first state to grant women the right to vote in 1869. This is a pivotal moment in Wyoming's history and is still celebrated today.

3. Yellowstone National Park: On December 21, 1936, President Franklin D. Roosevelt issued a proclamation that placed the vast majority of Yellowstone National Park within Wyoming's borders. The park spans over 2.2 million acres and includes Wyoming, Montana, and Idaho.

4. Powder River Expedition: During the winter of 1865-1866, General Patrick Connor led a military expedition called the Powder River Expedition. It was intended to put an end to the violence between Native Americans and white settlers in the region. The expedition lasted from December 21, 1865, to March 1866.

5. Coal Mining Disaster: On December 21, 1985, a methane gas explosion at the Wilberg Mine in southeastern Utah killed 27 Wyoming coal miners. The incident was one of the deadliest mining disasters in Wyoming's history and brought attention to the dangers of coal mining.