The undated photograph below was taken by O.V. Hunt, and shows the Railroad Reservation looking west across the Southern Railroad freight houses. In the near view is the 21st Street or "Rainbow" viaduct, opened in May 1919. The bridge is dedicated to members of the 167th Infantry Regiment, a part of the famed World War I "Rainbow" division. The large building in the distance was the Crane Company's plumbing supply house.
The vehicles in the photo would seem to indicate the picture was taken before 1940.
Source: Birmingham Public Library Digital Collections