This photgraph is in the Pratt/Magee Family collection (WH636). It was taken during the civil war and that the wagons in the foreground are ambulances. It is accompanied by a photograph of a soldiers home in Camp Nelson, Kentucky. Both photos are 8x10" albumen prints mounted on 10.5x12" cardstock.
Both pictures were taken at Camp Nelson, near Lexington probably in 1864. Copies of both images can be found (along with more than a dozen others) on the Camp Nelson website http://www.campnelson.org/tour/index.htm 
We appreciate the assistance in identifying this photograph especially the folks who frequent the True West website - http://truewest.ning.com/forum/topics/can-you-identify-this