Florida Keys113 miles of US-1 from Key Largo to Key West, 42 bridges, and the only living coral reef in the continental U.S.

The Florida Keys begin at Key Largo (MM 113) and end at Key West (MM 0), a 113-mile drive on US-1 that takes about 3.5 hours nonstop and ten times that with the right stops. Henry Flagler's Florida East Coast Railway opened the original Overseas Railroad on January 22, 1912 — the 1935 Labor Day Hurricane destroyed it, and the state rebuilt the right-of-way as the Overseas Highway four years later. The current Seven Mile Bridge (6.79 miles, 1982) parallels Flagler's original, which is now a fishing and biking pier.

Each segment of the chain has its own personality. Key Largo (MM 113–90) is the dive capital, home to John Pennekamp Coral Reef State Park — the first underwater park in the United States, opened in 1963 — and the Christ of the Abyss statue in 25 feet of water on Dry Rocks reef. Islamorada (MM 90–73) is the sportfishing hub; the Lorelei Cabana Bar at MM 82 sells the most photographed sunset frozen drink in the Keys. Marathon (MM 65–47) hosts the Turtle Hospital and the Seven Mile Bridge access. Big Pine Key (MM 33–29) is the Key deer refuge — a subspecies that grows to about 70 pounds. And Key West (MM 4–0) is the southernmost city in the continental U.S., 90 miles from Cuba, with Hemingway's house, Mallory Square sunset, and Duval Street.

Plan five to seven days to drive the chain end to end with real stops. Book Bahia Honda State Park camping or the Hawks Cay Resort early — both fill 11 months out for the December–April high season. Sunblock, polarized sunglasses, and reef-safe sunscreen (mandatory by Key West ordinance since 2021) are non-negotiable. The Dry Tortugas day trip from Key West — 70 miles further west, only reachable by ferry or seaplane — is the single best day in the Keys for anyone who's already done the standard chain.