Here are five interesting facts about December 13 in Colorado history:

1. On December 13, 1886, the Colorado Labor Wars began with a violent clash between striking coal miners and National Guard troops at the Rockvale Coal Company in Fremont County. The war lasted for years, with multiple casualties on both sides.

2. In 1978, the deadliest aviation accident in Colorado history occurred on December 13. A United Airlines DC-8 and a TWA Boeing 727 collided mid-air over New York City and crashed into a residential area in Adams County, killing all 44 passengers and crew members on both planes and 16 people on the ground.

3. On December 13, 2013, the Arapahoe High School shooting took place in Centennial, Colorado. A student entered the school armed with a shotgun and opened fire, injuring two students before taking his own life.

4. December 13, 1861, marked the founding of the Colorado Territory, which at the time included parts of present-day Colorado, Wyoming, Utah, and New Mexico. The territory was established by President James Buchanan in the midst of the Civil War.

5. In 1870, the Denver & Rio Grande Railroad completed a rail line from Denver to the mining town of Leadville on December 13, opening up new opportunities for transportation and commerce in the state.