1. On September 3, 1870, the Colorado State Agricultural Society held its first annual fair in Denver. The event showcased the state's thriving agricultural industry and included contests for the best crops, livestock, and farm machinery.

2. In 1915, the Colorado National Guard was called in to quell a labor dispute in the coal mining town of Ludlow. The conflict resulted in a violent confrontation between striking miners and the National Guard, which ultimately led to the deaths of dozens of people, including women and children.

3. On September 3, 1961, the new Denver Broncos football team played its first game in the American Football League, losing 13-10 to the Boston Patriots. The Broncos would go on to become one of the most successful NFL teams in history, winning two Super Bowls and producing some of the sport's most iconic players.

4. In 1984, the Colorado State Capitol building was designated as a National Historic Landmark. The building, which was completed in 1894, is a significant example of neoclassical architecture and serves as the seat of government for the state of Colorado.

5. On September 3, 2013, massive flooding devastated many parts of Colorado, causing widespread damage and claiming the lives of several people. The flooding was caused by heavy rainfall and resulted in evacuations, road closures, and power outages across the state. Despite the destruction, Colorado residents rallied together to support each other and begin the rebuilding process.