Tango Key is a fictional island 12 miles west of Key West. It's a rather mysterious place, with a long, rich history more intimately connected to that of the Caribbean than to Florida. Its topography is unlike anything else in the keys, with hills and cliffs at the north end of the island that gradually slope down to sea level at the south end. The oldest structure on the island is the lighthouse that faces the Gulf of Mexico. It was built in 1661, so it's nearly as St. Augustine, Florida, the oldest city in the U.S.
There are two main towns on the island - Pirate's Cove to the north and Tango to the south. The bridge, an engineering marvel that connects Tango to Key West and the others keys, is on the east side of the island. In the years before the bridge was built, residents on the island got to and from the other keys by car ferry, private boats, or by small plane. The commercial flights to Tango these days are on puddle jumpers. The airstrip isn't long enough to accommodate jets.
Tango Key also put in appearance in Esperanza and in Mistress of the Bones, the tenth book in a series featuring Quin St. James and Mike McMcCleary.