William J. Herrmann was a very knowledgeable physical culturist who taugh and heavily influenced Alan Calvert (in fact, Calvert's classic book "Super Strength" is dedicated to him.)
Herrmann's gym, once located at 1325 Chestnut Street in Philadelphia, Pennsylvania, was one of the popular hangouts for many of the strength stars of the early 20th century, most notably Sig Klein and Milo Steinborn, who performed a number of strength feats there. Sandow trained at Herrmann's place whenever he visited the US. At Hermann's, classes were taught in boxing, wrestling, fencing, body-building, calisthenics, Indian Clubs, gymnastics and acrobatics.
This picture was taken in 1931 and shows Milo Steinborn getting in a quick workout on the newly added open air section of the gym (used for hand ball and training in the fresh air and sun shine, among other pursuits.) Herrmann's son (also named William) won the bronze medal in tumbling at the 1932 Olympic Games in Los Angeles.