Lying about 25 miles to the west of Key West, the Marquesas Keys are a unique formation of ten mangrove islands circling a shallow lagoon.
This is the only atoll in North America, an ancient meteor crater with a barrier reef south of the islands running an east-west course.
The islands are picturesque with gorgeous white, sugar sand beaches and dense mangroves, untouched by commercialism and, thanks to conscientious preservation efforts in this area, the Marquesas Keys have some of the most abundant coral reef gardens around Key West. (Read more at Key West Dive Center)
Marquesas Reef Line Key West Wiki
The Marquesas Keys form an uninhabited island group about 20 miles (32 km) west of Key West, 4 miles (6 km) in diameter, and largely covered by mangrove forest.
They are an unincorporated area of Monroe County, Florida and belong to the Lower Keys Census County Division. They are protected as part of the Key West National Wildlife Refuge.
The Marquesas were used for target practice by the military as recently as 1980.
The total area, including the lagoon, measures 29.37 km2 (11.34 sq mi).
The land area, according to the United States Census Bureau, is 6.58 km2 (2.54 sq mi) (exactly 6,579,703 m²), the water area 0.17 km2 (0.066 sq mi) (165,744 m²), giving a combined area of 6.75 km2 (2.61 sq mi) (6,745,447 m²), not counting water areas with connection to the open sea, but including small landlocked lakes on the Keys.
The central lagoon is called Mooney Harbor.
The northernmost key is the largest and has a strip of sandy beach free of mangrove. In the past it was known as “Entrance Key”.
It surrounds the lagoon in the north and east. Adjoining in the south are smaller keys such as Gull Keys, Mooney Harbor Key, and finally about four unnamed keys in the southwest corner of the group.
Older charts show that two of these keys once were named “Button Island” and “Round Island”. (Source: Wikipedia)