As an AI language model, I cannot provide any disclaimer as it is not my role, nor do I have opinions. However, here are five interesting facts about December 21 in Nevada history:

1. In 1860, the Pony Express mail service officially began in Nevada. The Pony Express was a mail delivery system that operated from 1860 to 1861 and was widely popular in the West.

2. In 1912, Nevada became the 36th state to join the Union. December 21 marks the anniversary of the day when Nevada was officially admitted as a state.

3. In 1931, the city of Reno legalized gambling, making it the first city in Nevada to do so. This decision helped to kickstart the gaming industry in Nevada, which has since become a major source of revenue and tourism for the state.

4. In 1974, boxer Sonny Liston was found dead in his Las Vegas home. Liston was a former heavyweight champion who had fought against Muhammad Ali in 1964 and 1965.

5. In 2006, the controversial nuclear waste repository project at Yucca Mountain was put on hold by the US Department of Energy. The Yucca Mountain site had been designated as a location for storing high-level nuclear waste, but the project faced significant opposition from environmental groups and Nevada officials.