The Florida Keys are a chain-like cluster of about 1700 islands in the southeast United States. They begin at the southeastern tip of the Florida peninsula, about 15 miles (24 km) south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry Tortugas.
The islands lie along the Florida Straits, dividing the Atlantic Ocean to the east from the Gulf of Mexico to the west, and defining one edge of Florida Bay.
At the nearest point, the southern tip of Key West is just 94 miles (151 km) from Cuba.
The Keys were long accessible only by water. This changed with the completion of Henry Flagler's Overseas Railway in the early 1910s. Flagler, a major developer of Florida's Atlantic coast, extended his Florida East Coast Railway down to Key West with an ambitious series of over-sea railroad trestles.
The Florida Keys and Florida Reefs are of sand, shell, and coral formation. The reefs have frequent shoal patches. Together, they form the N boundary of the Straits of Florida. Toward the W end are several openings between the keys offering passage from the straits into the Gulf.