U.S. Route 66 became the first U.S. highway to be fully paved in 1938.
When Route 66 was designated in 1926, much of the route remained dirt, gravel, or otherwise unimproved. Completing the road required coordinated work across eight states, including bridge construction, grading, drainage, and concrete or asphalt surfacing.
The improvement made Route 66 more practical for long-distance motorists and helped establish its importance during the Dust Bowl migration and the growth of automobile tourism. Arizona’s entire section was also paved by 1938, although another highway had already claimed Arizona’s narrower distinction as the state’s first fully paved U.S. highway.
A common mix-up is confusing the route’s designation date with its paving date. Route 66 was established in 1926 and signed in 1927, but full paving came more than a decade later. The achievement helped support the route’s later image as a dependable transcontinental road.