The Mule Keys is a group of scattered islets between 3 and 12 miles (5-20 km) west of Key West, separated from it by Northwest Channel. On the west, they are separated from the Marquesas Keys by 6 mile (10 km) wide Boca Grande Channel. They belong to the outlying islands of the Florida Keys. Administratively, they are unincorporated area of Monroe County, Florida. The islets all part of Key West National Wildlife Refuge. The area of the islets totals 1.07 mi² (2.77 km²), of which 1.02 mi² (2.63 km²) are land area and 0.05 mi² (0.14 km²) inland water bodies (on three of the keys). The islets are uninhabited except Mule Key, for which the census of 2000 lists one housing unit with a population of two (park rangers or coast guard).

The United States Government has placed most of this area off limits, as a part of the Key West National Wildlife Refuge. It is even prohibited to anchor off Man Key and Woman Key in the sand, although Woman Key was a popular destination for day trippers from Key West in the past, which Boca Grande Key still is. Anchoring off the south part of Boca Grande Key is also prohibited; it is permitted only off the northwest portion. [1]

Ballast Key is privately owned and offered on the real estate market for US $13,800,000, as of February 2008 [2].

The easternmost islet, Mule Key, is 2.7 miles (4.4 km) west of Sunset Key which is part of Key West city. The westernmost (and largest) islet, Boca Grande Key, is 6 miles (10 km) east of the Marquesas Keys.