Florida was a disputed possession of England, France, and Spain in turn until it finally became a possession of the United States in 1821. A board of land commissioners for West Florida was established in 1822 and for East Florida in 1823 to process claims to lands previously granted by other nations. These documents, as well as land ancestries and homestead records, are at the Florida State Archives.
Baker Block Museum: a project of the North Okaloosa Historical Association. Many family histories have been submitted in the form of notebooks and published books. Out of print books on topics of historical interest are available. Photographs of individuals, families, and county history are also preserved, along with old maps, microfilms of early newspapers, etc.
Heritage Museum in Valparaiso: A modest collection of books and publications on the history of Florida and the Florida Panhandle are available for review (by appointment, only). Some city directories are available. A card index of locally published obituaries contains over 10,000 names. New publications range in subject from regional recipes to local history and are available for sale.
Archaeology site lists other historical organizations, also. Occasionally, family histories are archived at these sites.
Find which county a town is in, what town a cemetery is in, even where a postoffice or building is by using the United States Geographical Survey's Geographical Names Information System.
David Rumsey Map Collection is a large online collection of rare, old, antique historical atlases, globes, maps, charts plus other cartographic treasures.