Harding Circle Historic District
The Harding (St. Armands) Circle Historic District received registration on the National Register of Historic Places on January 16, 2001. It encompasses the Harding Circle Park, adjacent medians along John Ringling Blvd. and the Boulevard of the Presidents, and associated Ringling-era statuary.
The application for historic registry can be found here. From that web page you can link to this PDF which contains a detailed write-up of the history of St. Armands and John Ringling's activity here, along with a bibliography of sources and footnoted references.