What U.S. route carries the Overseas Highway through the Florida Keys?

U.S. Route 1 carries the Overseas Highway through the Florida Keys. The highway links the mainland near Florida City with Key Largo, the Middle Keys, and Key West along the island chain.

The modern road follows much of the route created after the collapse of Henry Flagler’s Florida East Coast Railway extension in the 1930s. The Overseas Highway opened in 1938, using surviving railroad bridges and the former rail corridor where practical. Its bridges and causeways connect a series of islands across Florida Bay and the Straits of Florida.

A common mix-up is treating the Overseas Highway as a separate numbered federal route. “Overseas Highway” is the road’s descriptive and historic name, while U.S. 1 is its official route designation through the Keys. The route is also associated with mile markers that count down toward Key West, helping travelers navigate the long chain of islands.