The State of Florida began to purchase large tracts of land for the preserve in 1995. The primary purpose of acquiring the land was to protect the watershed to the St. Sebastian River and the Indian River Lagoon and soon grew to include protecting rare and endangered species of plants and animals and the pristine habitats where they live. The preserve covers one-third of the watershed to the St. Sebastian River, improving water quality and reducing human impacts such as agricultural and residential uses. The preserve has grown continually since the first land acquisition and now encompasses more than 35 square miles (22,000 acres).