Located on U.S. Highway 1 between mile markers 75--78.

Matecumbe la Viejo on most Spanish charts. Matacunbe Nuebo on 1733 Nueva Espana shipwreck chart. Matacombe la Viega on DeBrahm chart (1772). Vieja Matacomb on Romans chart (1774). Old Matecumbe on Gauld chart (1775). Survey maps drawn in 1872 by Charles Smith show Lower Metacumbe Key. A book written in 1925 by Wendell Endicott uses the name South Matacumbe.

This key is the site of a number of Indian mounds and middens, most of which were destroyed during the building of the Florida East Coast Railway. A number of natural wells were also located here, at the northeast end of the key. These wells were well known to early seafaring men as the most reliable source of fresh water in the Keys. They, too were destroyed during the railroad era, and the location of their site has been lost. The southwestern end of the key is the site of a former sand mining operation.