Hoepfner studied at the Beaux Arts Institute of Design, NYC, where he subsequently became an instructor, as well as a member of the Jury of Award.

He was acclaimed for his class titled "Architectural Ornament" and in 1925 was invited to become an honorary member of the Beaux-Arts Institute of Design.

Hoepfner also studied at the National Sculpture Society and George Bridgman Institute in New York City, where he was recognized for having achieved the status of anatomical perfection.

He is recognized for his work on the bronze panels in the front doors of the Detroit Public Library, Main Branch.

He is documented in the book Masterpieces of American Architecture,[1] and for this work Oswald is listed in the Smithsonian Institution's Inventories of American Painting and Sculpture [2] Oswald is also recognized in the July 1921 issue of Architectural Forum magazine [3] for his work on the niche in the Cunard Building, NYC.