1) On July 17, 1899, the Denver Tramway Company began operation of its first electric streetcar line in Denver. The line ran along 15th Street, from Broadway to City Park, and marked a significant milestone in the city's transportation infrastructure.

2) July 17, 1955, marked the opening of Elitch Gardens in its current location in northwest Denver. Originally founded in 1890 in another part of the city, the amusement park has provided generations of Coloradans with entertainment and thrills.

3) In 1964, the Colorado State Fairgrounds in Pueblo hosted a concert by the Beatles, which drew over 20,000 fans. The concert, which was part of the band's first U.S. tour, marked a significant moment in both Colorado and music history.

4) On July 17, 1976, the United States Air Force Academy Chapel in Colorado Springs was dedicated. The striking, modernist building, which features 17 spires that reach 150 feet into the sky, has become one of the most iconic landmarks in Colorado.

5) In 2001, the town of Bailey, Colorado, was rocked by a tragedy when a lone gunman entered Platte Canyon High School and took seven girls hostage. The standoff ended with the gunman fatally shooting one of the hostages before taking his own life. The incident sparked a nationwide debate about school safety and gun control.