Matecumbe Key Real Estate for sale Upper Matecumbe Key is an island in the upper Florida Keys. U.S. 1 (or the Overseas Highway) crosses the key at approximately mile markers 79—83.5, between Windley Key and Lower Matecumbe Key. All of the key is within the Village of Islamorada as of November 4, 1997, when it was incorporated.The island lies to the southwest of Windley Key, and to the northeast of Lower Matecumbe Key. Lower Matecumbe Key is an island in the upper Florida Keys. It is located on U.S. 1 between mile markers 75--78. All of the key is within the Village of Islamorada as of November 4, 1997, when it was incorporated. It is home to the main base of the Florida National High Adventure Sea Base. The island lies to the southwest of Upper Matecumbe Key, and to the northeast of Craig Key.