Florida Keys, a series of islands, extending in the form of a crescent 220 m. S. W. along the S. coast of Florida, beginning near Cape Florida, and ending in the Dry Tortugas, belonging partly to Dade and partly to Monroe county; pop. in 1870, 5,553. They lie between the mainland and the Florida reefs, and from 3 to 5 m. from the Gulf stream. They are very numerous, and vary in extent from a few acres to 25 sq. m. Cayo Largo (Long Key) is the largest of these islets (about 30 m. long and 1/2 m. to 5 m. wide), and Key West the most important. They lie but a few feet above tide water, are of a uniform coral formation, very rocky, and mostly covered with a growth of hard wood.