1. On September 18, 1890, the first Colorado State Fair was held in Pueblo. It attracted over 10,000 people and featured a variety of exhibits, livestock shows, and carnival rides.

2. On September 18, 1928, a massive flood hit the city of Boulder, killing six people and causing millions of dollars in damage. The flood was caused by heavy rainfall that overwhelmed a dam in the nearby mountains.

3. On September 18, 1984, astronaut Kathy Sullivan, a native of Paterson, New Jersey, became the first American woman to walk in space. She accomplished the feat during the Space Shuttle Challenger's STS-41G mission.

4. On September 18, 2013, the Colorado Department of Revenue announced that the state had surpassed $1 billion in cannabis sales since the legalization of recreational marijuana in 2012. This made Colorado the first state in the US to reach this milestone.

5. On September 18, 2018, Colorado Governor John Hickenlooper signed an executive order establishing the state's new Office of Saving People Money on Health Care. The office is tasked with finding ways to reduce healthcare costs for Coloradans and increase transparency in the healthcare industry.