Thomas Sully was born in Mississippi City, Mississippi, the great nephew and namesake of the English-born artist renowned for his American portraits and history paintings. The younger Thomas Sully obtained his early education at Dr. Sander’s School in New Orleans, followed by architectural apprenticeships with Larmour & Wheelock (Austin, Texas) and then J. Morgan Slade & Henry Rutgers Marshall (New York City).
Read more about the architect in the online finding aid here.
If you are unfamiliar with the Southeastern Architectural Archive's holdings, consult its list of "Finding Aids by Collection Name."
Image above: Thomas Sully, architect. The Medical Building, 124-126 [formery 17-19] Baronne Street. As it appears in New Orleans Through a Camera, Louisiana Research Collection, Special Collections Division, Tulane University Libraries.