Costin, William, 1780?-1842

William Costin was a prominent free black man in early 19th-century Washington DC. He was a messenger for the Bank of Washington and ran a hack business in the city. In 1800, he married his cousin Philadelphia (“Delphy”), a dower slave of Martha Washington. Upon Martha Washington’s death in 1802, Delphy became the property of Eliza Parke Custis Law, wife to Thomas Law. Delphy and their children were granted freedom shortly after, and the couple decided to stay in Washington, D.C. Together the Costins had seven children. He died in 1842

William "Billy" Costin (c. 1780 - May 31, 1842) was a free African-American activist and scholar who successfully challenged District of Columbia slave codes in the Circuit Court of the District of Columbia.Little is known of Costin's upbringing. His enslaved mother was Ann Dandridge-Costin, and her father is reputed to have been Col. John Dandridge of Williamsburg, Virginia,[3][4] making her the half-sister of Martha Washington.