Old Atlanta newspapers, from UGA microfilm collection, are available, and searchable, for free on http://atlnewspapers.galileo.usg.edu/atlnewspapers/search
From the "Daily Intelligencer" of 27 Feb 1866, on Page 2:
"we learn that the Senate has passed a bill establishing a 'Georgia State Orphan Home,' to be located in this city, and to be the property of, and under the exclusive management of the State."
That's the first post-war mention I found, but searching on the term returns many further articles.