I found this newspaper article in the vertical file.
Remains of Fort Fanning were visible in 1958, and were bulldozed to build the subdivision. The article shows that they knew what it was. Such a shame, because this would have been one of the best archaeological sites of Seminole War forts.
But, the cisterns might still be under the ground.
The photo is hard to see, but it shows a brick well or cistern surround by grass.
The Gainesville Daily Sun--Gainesville, Florida, April 29, 1958.
Fort to Subdivision?--About 10 acres in the vicinity of Fort Fanning eight miles west of Trenton on the banks of the Suwannee are being bulldozed, plowed and graded with streets platted for a future subdivision. The brick cistern structure in the center of this wooden area is the only remains of the wooden fort used about 1837-38 in the Seminole War. [Actually until the end of the war in 1842.]
The cistern is about 12 feet deep and about three feet across the top. Of brick and masonry construction, it was used for water storage inside the walls of the from, named for Captain Fanning. [Actually, Lt. Colonel Alexander C.W. Fanning.]
This location, near Fanning Springs, is about 250 yards from U.S. 19. Cone brothers Construction Co, Tampa, have started development of the property which it owns.