Located on U.S. Highway 1, at approximately MM 86--91, between Windley Key and Tavernier.

Unnamed on Spanish charts. Most early Spanish cartographers considered Plantation Key part of Key Largo. DeBrahm chart (1772) shows Bull Isle. Gauld-Faden chart (1775) shows Long Island. J.W. Norie, In his "Piloting Directions for the Gulf of Florida, the Bahama Banks, & Islands" (1828) states: "This island has no name given to it, either by the Spaniards or the Providence people, but goes under the general appellation of Cayo Largo, from which it is separated by a narrow channel; (Tavernier Creek) it is distinguished in our chart by the name of Long Island." Blunt chart (1846) shows Long Island. Gerdes, in his "Reconnaissance of the Florida Reefs and All the Keys" (1849) states: "The island below Cayo Largo now called on chart Long Id. is called Plantation Island for the fact of there having formerly been here a plantation belonging to English wreckers from Abaco Island." A survey map drawn by M.A. Williams in 1872 shows Plantation Key.

Before the Flagler railway crews filled Little Snake Creek, which crossed at a point around today's Treasure Harbor, the southwest end of Plantation Key was a separate island known as Snake Creek Key. Plantation Key is the site of a number of prehistoric Indian sites and mounds, most of which have been destroyed by development. An early settlement on the Oceanside was known as Pearl City for a large conch pearl found by John Lowe.