- 1909: The first highway bill was passed by forming a three-member Highway Commission to approve work and allocate funds. The Commission first took their post on January 1, 1910.
- 1917: The State Highway Fund was created and a State Highway Department (CDOH - Colorado Department of Highways) was formed.
- 1935: Highway Department employees were joined by 44 new co-workers selected from among 7,500 applicants to become the first members of the Colorado State Highway Courtesy Patrol. The Patrol became a division of the Highway Department.
- 1947: The first National System of Interstate and Defense Highways was approved by the federal works administrator. In Colorado, approved routes included all of I-25 from the Wyoming border to Raton Pass; all of I-80S (now I-76); and I-70 from Denver to the Kansas border.
- 1953: The state legislature passed a new law reorganizing the Highway Department and renaming it the Colorado Department of Highways.
- 1956: Congress passed the Federal Interstate Highways Act. Among the approvals was the section of I-70 from Denver to the Utah border.
- 1991: CDOH became Colorado Department of Transportation (CDOT)
- 2010: CDOT celebrates its 100-year anniversary
