1. Rocky Mountain National Park was established on July 28, 1915, becoming the tenth national park in the United States. The park, which spans over 415 square miles in north-central Colorado, is home to some of Colorado's most iconic natural features, including towering peaks, alpine lakes, and deep forests.

2. On July 28, 1976, Colorado hosted the Democratic National Convention in Denver. It was the first time a major political party had held its convention in the Rocky Mountain region, and it brought a significant amount of attention and tourism to the city.

3. Denver's Red Rocks Amphitheatre, one of the most iconic concert venues in the world, was officially dedicated on July 28, 1941. The natural amphitheatre, located just outside of Denver in the foothills of the Rockies, has hosted some of the biggest names in music over the years, from The Beatles to U2 to Mumford & Sons.

4. The Colorado Territorial Correctional Facility in Canon City, Colorado, opened its doors on July 28, 1871. The prison is still in operation today, housing over 3,000 inmates at any given time, and has been the site of some of Colorado's most infamous criminal cases, including those of murderers Ted Bundy and Alfred Packer.

5. On July 28, 1861, near the beginning of the Civil War, a battle took place in southern Colorado at Apache Canyon between Confederate and Union forces. The battle, which lasted for three days, was ultimately won by the Union Army, and it helped to secure the western territories for the Union.