Long Key is an island in the middle Florida Keys. Long Key was called Cayo Víbora (Rattlesnake Key) by early Spanish explorers, a reference to the shape of the island, which resembles a snake with its jaws open, rather than to its denizens. The city of Layton is located on Long Key. The 965-acre (3.9 km2) state park (3.9 km²) was dedicated October 1, 1969.
U.S. 1 (or the Overseas Highway) crosses the key at approximately mile markers 65.5--71, between Fiesta Key and Conch Key. It is the home of Long Key State Park, a favorite of campers and nature lovers, the camp sites are on the beach but the proximity of US1 makes it noisy. It is smaller and less developed than the neighboring incorporated village of Islamorada to the northeast and city of Marathon to the southwest.
It was visited by C.W. Pierce in his boat, Bonton (1885). He stopped at the lower end of the key where there was a house with a cistern and replenished his water supply.
The key was a depot site during the railroad years, and was also the site of the well known Long Key Fishing Camp.