1. In 1850, the first permanent settlement in what is now known as Colorado Springs was established. A group of 15 men arrived at the site on June 25 and began to lay out plans for the town. It was originally called Fountain Colony and was later renamed Colorado Springs in 1871.

2. On June 25, 1876, a group of Sioux and Cheyenne warriors fought against the United States Army in the Battle of the Little Bighorn, also known as Custer's Last Stand. The battle took place in Montana, but many of the soldiers involved were from Colorado.

3. The Colorado Labor Wars were a series of strikes and conflicts between miners and mining companies in the late 19th and early 20th centuries. On June 25, 1903, the Victor-American Fuel Company fired over 300 miners in the southern Colorado town of Walsenburg. This led to a strike and eventually the Colorado National Guard was called in to break it up.

4. The Rocky Mountain Arsenal was a U.S. Army chemical weapons manufacturing facility located near Denver. On June 25, 1969, a nuclear reactor was installed at the arsenal as part of a research program. It was used to produce tritium, a radioactive isotope used in nuclear weapons.

5. In 2011, the Colorado Department of Transportation opened the new Twin Tunnels on Interstate 70 near Idaho Springs. The tunnels are part of a project to widen the highway and improve safety in the area. The project took several years to complete and cost over $100 million. The tunnels were officially opened on June 25, 2013.