Nathan Francis Mossell was the first African-American graduate of the University of Pennsylvania School of Medicine in 1882. He did post-graduate training at hospitals in Philadelphia and London. In 1888, he was the first black physician elected as member of the Philadelphia County Medical Society in Pennsylvania. He helped found the Frederick Douglass Memorial Hospital and Training School in West Philadelphia in 1895, which he led as chief-of-staff and medical director until he retired in 1933. Gertrude Bustill Mossell was his wife.

Sadie Tanner Mossell Alexander was a pioneering Black professional and civil rights activist of the early-to-mid-20th century. In 1921, Mossell Alexander was the second African-American woman to receive a Ph.D. and the first one to receive one in economics in the United States. In 1927, she was first Black woman to receive a law degree from the University of Pennsylvania Law School and went on to become the first Black woman to practice law in the state. She was also the first national president of Delta Sigma Theta sorority, serving from 1919 to 1923.