Which interstate highway largely replaced U.S. Route 66 across Arizona?

Interstate 40 largely replaced U.S. Route 66 across Arizona.

Route 66 ran east–west across northern Arizona, passing through Kingman, Seligman, Flagstaff, Winslow, and Holbrook before reaching New Mexico. As Interstate 40 was built and completed, much of the older highway was bypassed, abandoned, or incorporated into the newer interstate’s alignment.

The change had major consequences for towns that depended on Route 66 travelers. Traffic shifted away from many small communities, contributing to business closures and the decline of roadside attractions. Arizona’s Route 66 designation was retired in 1984, while the route was retired nationwide the following year.

The replacement was not exact everywhere. Between Kingman and Seligman, for example, I-40 follows a more southerly and direct path, leaving a substantial stretch of old Route 66 outside the interstate corridor. Today, surviving sections are promoted as Historic Route 66, and several former alignments remain important tourism routes during the road’s 2026 centennial.