Located on U.S. Highway 1, mile markers 65--71, between Lower Matecumbe Key and Duck Key (II).

Spanish charts show Cayo Vivora or Bivora - SP. "Rattlesnake Key" The 1733 shipwreck charts show Cayo Vivora. Juan Elixio de la Puente chart (1765) shows Vivoras. Romans chart (1774) shows Cayo Vivora DeBrahm (1772) shows Veveras. Long Key is mentioned in the log of the British ship Bustard for the year 1823. Both Gauld (1775) and Blunt (1846) show Cayo Bivoras or Viper Kay. Gerdes, in his "Reconnaissance of the Florida Reefs and all the Keys" (1849) states: "The name of Vipar Key, or Cayo Bivoras is not known to anybody, but the island is called Long Island." Survey maps drawn by Charles Smith in 1872 show Long Key.

Visited by C.W. Pierce in his boat, Bonton (1885). He stopped at the lower end of the key where there was a house with a cistern and replenished his water supply. This key was a depot site during the railroad years, and was also the site of the well known Long Key Fishing Camp.