Green Mound is one of the best preserved and last remaining shell mounds in the region, preserving the history of prehistoric Florida Indians who inhabited the site for hundreds of years. Archaeological studies date artifacts there to the St. Johns period from 500 BC to 1565 AD. Mounds like this typically contain discards from daily life such as bones, shells, pottery, and tools. Studies show that during the St. Johns I period, from 500 BC to 800 AD, people occupied the site year round, while during the St. Johns II period, from 800 AD to 1565 AD, people may have occupied it seasonally. A botanical survey of Green Mound by John K. Small in 1922 found a unique botanical environment that included several rare plant species, and some of the species he noted, including wild-coffee, marlberry, and snowberry, are still visible around the mound. By 1933, a significant portion of the mound had been mined for shells used in road construction. In 1948, the Green Mound Historical Society, led by R.J. Longstreet, recognized its significance, purchased it for preservation, and turned it over to the Florida State Board of Forestry.