As the ice age ended large amounts of melting glacial ice led to rising sea levels. As part of this long term process the Florida shoreline moved 20 to 100 miles landward, and Manasota Key and many other barrier islands were formed. For most of its life Manasota Key remained pristine and largely undeveloped. However, during the 1900s things started to change in Florida. The State experienced large scale development and huge population growth. This included a relentless push to the sea by developers and residents.