Although Spain agreed to cede Florida to the United States in 1819, the transfer did not take place until 1821; so the territory was not represented in the United States census of 1820. The first statistical account of its population, therefore, is that of 1830.
Harper, Roland M.
"Ante-Bellum Census Enumerations in Florida,"
Florida Historical Quarterly: Vol. 6
, Article 8.
Available at: https://stars.library.ucf.edu/fhq/vol6/iss1/8