Webb was born on May 6, 1852, in Tarrytown, New York.Henry Walter Webb passport application from 21 May 1890 He was the son of James Watson Webb (1802–1884), a United States Minister to Brazil, and his father's second wife, Laura Virginia Cram (1826–1890). Among his siblings was brother Dr. William Seward Webb, who was married to Eliza Osgood Vanderbilt; and Alexander Steward Webb, the longstanding President of City College of New York.
