Northeast of downtown Bradenton, this is the oldest structure on the southwestern coast of Florida, and a fine example of an antebellum plantation home -- something that's rare in Florida. It was constructed during a 6-year period in the late 1840s by Maj. Robert Gamble, made primarily of "tabby mortar" (a mixture of oyster shells, sand, molasses, and water), with 10 rooms, verandas on three...