- Interstate first signed and showed up on Colorado maps in 1961.
- Highest point on Interstate system is at the Eisenhower Tunnel. – 11,155 feet. Also, it’s the highest vehicular tunnel in the United States.
- The last section of interstate highway to open in Colorado was I-76 between Pecos Street and I-25, in September 1993. Completion of this segment marked the completion of the interstate system in Colorado.
- Colorado has 956 designated miles of interstate highway
- The I-70 Final Link segment in Glenwood Canyon was dedicated in October, 1992. That completed the mainline interstate system (excluding connector interstates) in the U.S. This 12.5 mile segment includes 40 bridges and viaducts, three tunnels, 15 miles of retaining wall, four full-service rest areas and a bikepath.
- Colorado's interstate highway system comprises 10% of the total state highway system, yet 40% of the 43.5 billion miles of Colorado vehicle travel annually take place on the interstate system
- The first segment of freeway in Colorado, later to become I-25 when the federal law creating the interstate highway system was passed in 1956, was a 2 mile segment of the Valley Highway in Denver, which began construction in August, 1948, and was completed in 1950. The entire segment of Valley Highway north-south through the Denver metro area was completed in 1958.
- A 9.2 mile segment of freeway in Pueblo, later also to become a segment of I-25, began construction in 1949 on the right of way of U.S. Hwys. 85/87 and was completed in 1958
- The first Colorado link of interstate highway with another state occurred on Oct. 11,1964, when a 26-mile segment of I-25 from Wellington, CO, to the Wyoming state line, was completed and opened.
- The first bore of a major highway tunnel through the continental divide on what is today's I-70 began in 1968. Completed in 1973, this was the current westbound bore of I-70, named the Eisenhower Memorial Tunnel. Its contract, for $54.14 million, was the larges single federal aid highway contract ever awarded in the United States up until that time.
- It took the new Eisenhower Tunnel only four months to carry its one-millionth vehicle; three months later, it carried its two-millionth vehicle