There are several historic outbuildings on the property of the Alexander Hotel. A sign indicates that this is the old post office from the Altamaha community.
Old Altamaha Post Office, Reidsville
Vanishing Georgia: Photographs by Brian Brown
Since 2008. A visual survey of Georgia's historic architecture and culture. 9,000 locations. 30,000 images.
Del Presley at Georgia Southern became quite an expert on structures like this when doing research for Project RAFT in 1982. I remember going to a place near Jesup or Odom where there was one of these moveable post office structures on skids, but by that time it was part of a pig pen. I went in, took lots of photos, and paid the price in terms of cleaning my boots. When I saw your photo, I recognized the design right away.