What are the chain islands of Florida that North largest coral reef?

The Florida Keys, officially the Monroe County, is an archipelago located off the southern coast of the U.S. state of Florida, consisting of more than 1,700 islands, of which only about 40 are populated. It begins near mainland Florida in Miami-Dade County and forms an arc stretching southwest and then south, ending at Key West, the westernmost major city in the contiguous United States. Key Largo is the northernmost major island. They include the third-largest coral barrier reef in the world, the Florida Reef, with a living coral area in excess of 58 mi², located about 7 mi (11 km) offshore, parallel to the island chain.