Main Key, Barnes Sound MAIN KEY is a 145.5-acre, private island, with pristine, white sandy beaches located in Barnes Sound, Ocean Reef area, in Monroe County, The Florida Keys. There is approximately 12 acres of upland elevation where a structure could be built and an active dock and lift permit to build on the East of the SE beach, from the Government Lot, with plans for a 295' long dock with a 20 ft platform for a lift and a 30' boat slip. A 2nd dock permit is being applied for on the South side of Main Key, which will be 135 feet with a 30 to 40 ft platform and seven heavy pilings to moor a large vessel or work barge up to 100 feet in length. There was a house built on the island at one time. ''The Tides of Main Key'' is well known in South Florida in Marine Weather forecasts on TV, Radio, NOAA weather, or online for tides in the Upper Keys and Key Largo. The tide station at Main Key was established in the 1930's and is still reported in the tide forecasts. Before online and smartphones, ''The tides at Main Key in Barnes Sound'' was a frequently reported tide station for the western bay waters of North Key Largo and is still reported online for projected tides as one of the official tide stations to this day.