William Henry Howell was born in Baltimore, Maryland. He graduated from the Baltimore City College high school in 1878. He attended Johns Hopkins University and graduated in 1881, then received his PhD in 1884. He taught at the University of Michigan and at Harvard before becoming professor at Johns Hopkins in 1893. In 1898 he became associate editor of the American Journal of Physiology. He was dean of the Johns Hopkins medical school from 1899 to 1911. He wrote Textbook of Physiology for Medical Students and Physicians (1905).