Signs for U.S. Route 66 were first erected in 1927, after the route was designated in 1926.
The highway was established on November 11, 1926, as part of the first nationwide U.S. Numbered Highway System. Designation gave the road an official number, but motorists still needed visible signs to follow its route across multiple states.
Route 66 was assembled from existing roads and trails, including portions of the National Old Trails Road and the Ozark Trails system. Because the roadway was not initially a single newly constructed highway, signing was an important part of making the Chicago–Los Angeles corridor usable as a continuous route.
The distinction between designation and signing is easy to miss. Route 66 legally entered the numbered system in 1926, while the recognizable highway signs appeared beginning the next year. The route remained partly unpaved for years afterward.