William Bradford was born in Philadelphia, Pennsylvania, on September 14, 1755. He received the degrees of A.B. and A.M. from Princeton University, and studied law under Edward Shippen. He volunteered as a private in 1776 and subsequently attained the ranks of lieutenant colonel, deputy quartermaster general, deputy muster-master general and colonel in the Continental Army.
Bradford was admitted to the bar of the Supreme Court in September 1779. In 1780 he was appointed attorney general of Pennsylvania, serving for the next eleven years. He served as justice of the Supreme Court of Pennsylvania from 1791 to 1794, when President Washington appointed him United States Attorney General. He died in office on August 23, 1795.