Hello Ken,
The person in question surname was spelled McMillan. He was living at "Scotch Bend" in Santa Rosa County, Fl at the time of the War- so I would assume he was elected to the Fla Govmt. He is buried at "Coon Hill Cemetery" near Scotch Bend, which is across the river from McDavid. He was in Co. E 15th Conf Cav. Or the " Simpson Mounted Rangers" I believe it was called before Capt Leigh took over and the 15th was formed from these independent Cav companies in Al and Fla. If you need any other info on this Duncan I have it so just let me know.