The son of Henry L. Richardson and Frances M. (Lincoln) Richardson, William King Richardson (1859-1951)was a lawyer and book collector. His library was left to the Houghton Library at Harvard. Roland Lincoln was his uncle. Richardson graduated from Harvard College in 1880 and went abroad with his family that summer, intending to travel with them, but instead he was persuaded to begin at Oxford that fall. He graduated in 1884 with a double first at Balliol. The following year, he entered Harvard Law School. Richardson was admitted to the Massachusetts bar in 1887 and was a member firm of Fish, Richardson and Neave, specializing in patent law.