It is a complex of mounds and accumulated shell, fish bone, and pottery middens that rises more than 30 feet above the waters of the bay.

The Calusa formed an extensive structure of mounds, water courts and canals whose features still exist today.

Mounds were constructed by the collection and organization of "midden" which is a collaboration of shells, fish and animal bone, and artifacts such as pottery.

Islands that were created by the Calusa, such as Mound Key are sometimes called "trash-heaps" as their composition is made from waste products of their culture.

They are not however, just "heaps of Calusa garbage" simply tossed aside, but intricate compositions of substrate that were used for a display of power, religious monuments, and as burial memorials.

It served for many years as the ceremonial center for their kingdom, which extended over numerous shell midden islands they made up and down the southwest coast of Florida.

The island was where King Carlos hosted a wedding for his sister, who was later baptized as Antonia, to Pedro Menéndez de Avilés, a political marriage meant to solidify an alliance with the Spanish.

[1] Their kingdom spanned from Tampa Bay southward to the Ten Thousand Islands and eastward to Lake Okeechobee.

Grandma Johnson remained at Mound Key and allowed several families — Luettich, Hawkins, Hanson and Fernandez — to build homes on the island.

By the turn of the 20th century, most all Mound Key settlers had moved up river to Estero, then a citrus and cow farming town.