Located on U.S. Highway 1 at approximately mile markers 79--83.5, betweeen Windley Key and Lower Matecumbe Key.

The 1733 Spanish wreck chart shows Matecumbe Viejo. Father Alaña's chart (1743) shows Matecumbe el Vieio. Juan de Liguera chart (1742) shows Matecumbe el Viejo. An unidentified 1760 chart shows Matecumbe el Biejo. The O'Carol chart (1770) shows Matecumbe el Viejo. DeBrahm (1772) shows Matacombe la Mosa. Gauld chart (1775) shows New Matecumbe. Blunt's American Coast Pilot (1842) uses Little Matecumbe. Blunt chart (1846) shows New Matecumbe. A survey map drawn in 1873 by Charles Smith shows Upper Metacombe Key.

The history of the names of both this key and Lower Matecumbe Key are very confusing, as identical names have been used at different times to designate both keys. Upper Matecumbe Key is the location of the original settlement site of Islamorada. There are a number of Indian mounds and habitation sites located here.