In April 1855, the Key Biscayne North Base Marker was placed here by the U.S. Coast Survey team under the direction of Alexander Dallas Bache, the great-grandson of Benjamin Franklin and Superintendent of the Coast Survey. The survey was done by triangulation, a mathematical system using triangles to compute various distances from a few measured lengths, known as bases. Using these bases, the coast of South Florida was mapped for navigational purposes. The north end of the Key Biscayne base is located 3.597 miles from the south marker, which is approximately 300 feet southeast of Cape Florida Lighthouse.