1. The Colorado Labor Wars began on March 31, 1903.
On this day, the United Mine Workers of America walked off the job in protest of poor working conditions and low pay. This led to a series of violent clashes between miners and mine owners, known as the Colorado Labor Wars, which lasted until 1914.

2. On March 31, 1931, the Boulder Dam (later renamed the Hoover Dam) was completed.
The dam, which spans the Colorado River between Arizona and Nevada, was a massive engineering feat and provided hydroelectric power and irrigation water to the Southwest region.

3. Colorado received its state nickname on March 31, 1876.
The state was officially recognized as the "Centennial State" in honor of the nation's centennial anniversary.

4. The deadliest avalanche in U.S. history occurred on March 31, 1911, in the town of Georgetown, Colorado.
A massive avalanche swept down from the mountains and destroyed much of the town, killing over 90 people.

5. On March 31, 1985, Denver International Airport broke ground on its construction.
The airport, which opened in 1995, is one of the largest in the world and covers over 34,000 acres. It is known for its unique design and controversial artwork, including the infamous "blue horse" statue.