James Thomas Flexner was born January 13, 1908, in Manhattan. His father was Simon Flexner, a sixth-grade dropout who became a self-taught microbiologist, pathologist, director of the Rockefeller Institute for Medical Research in New York City and discoverer of a cure for spinal meningitis. His mother was Helen Thomas [Flexner], a professor of English at Bryn Mawr whose sister was president of the college.[3][5] In 1929, Flexner graduated cum laude from Harvard University, and found work as a reporter for the New York Herald Tribune. In 1931, he took a position at the New York City Department of Health as an executive secretary. The following year, he left his job to devote his full energies to writing. Although untrained in art history, he gravitated to art subjects as part of his interest in writing about American history.[5]
Flexner is known best for George Washington, a four-volume biography published by Little, Brown from 1965 to 1972. He won a special Pulitzer Prize for the work in 1973.[2] He wrote other historical biographies, including The Young Hamilton (on Alexander Hamilton), Mohawk Baronet (on Sir William Johnson, 1st Baronet), and The Traitor and the Spy: Benedict Arnold and John André. He wrote many books on the history of American art, including a highly regarded life of the American painter John Singleton Copley. He and his father, Simon Flexner, M.D., co-wrote William Henry Welch and the Heroic Age of American Medicine (1941). (His uncle, Abraham Flexner, was the educator whose 1910 report led to the reform of United States medical schools.)
Flexner died February 13, 2003, at his apartment in New York City at the age of 95.[3]