Fort Davis isn't really elusive- it's big and it still exists- but until now there was only one photograph of it identified. It is beautifully captured in the background of LC 02607 and LC 02608. If interested, download the tif version from the LC website for a more high definition view, which is clear enough to show ladders at the base of a signal tree. The rectangular patterns in the grass- tent sites?
Fort Davis & Battery XXII
Fort Sedgwick, better known as Fort Hell