a fort and settlement, in an effort to colonize the area. A Jesuit mission was also founded there at the same time by Juan Rogel, a priest of that order. Called San Antón de Carlos, it was the first such mission in the Spanish New World. There was frequent conflict with the Calusa, though, and eventually the island was abandoned by the Spanish in 1569. The Spanish brought with them diseases to which the Calusa had no immunity. These diseases and warfare with the Spanish eventually ended the Calusa civilization around 1750. In subsequent years, the island was used and sometimes inhabited by pirates, fishermen (Cuban, Portuguese and Spanish), and American pioneers, among others. Frank Johnson and his wife, Grandma Johnson, were given a homestead on Mound Key in 1891. This marked a period of European immigration to the former Calusa capital. Grandma Johnson remained at Mound Key and allowed several families — Luettich, Hawkins, Hanson and Fernandez — to build homes on the island. She taught them to fish, to farm, how to build houses that would stay cool in the summer and protect them against Florida's abusive sun and summer storms. 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. The Johnsons sold the island to the Koreshans, a utopian cult, in 1905. In 1894, the followers of a scientific/religious belief system known as Koreshanity arrived in the area. They built a community based on their utopian ideas, growing over the next two decades. During this time, part of the property they acquired included most of the parcels on Mound Key. After the death of their leader, Cyrus Teed, in 1908, their numbers declined. In 1961, the remaining Koreshans decided to give over ownership of the key, as well as other land in nearby Estero, to the state. It was used to form the park, which is administered by the Koreshan State Historic Site. Approximately nine acres still remain privately owned by the McGee family. The McGee family agreed to sell their remaining parcel to Lee County in 2019. In 2020, archeologists confirmed that Mound Key was the site of Fort San Antón de Carlos. Which was a Spanish fort as well as one of the first Jesuit sites in North America. The fort was abandoned in 1569, after the Spanish-Calusa alliance