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 Costin was born approximately 1780, believed to be the son of Ann Dandridge-Costin, an enslaved woman. He 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 that would have required free Blacks in Washington City to post a bond and submit to annual registration.
His parentage is unclear; stories indicate he may have been a relation of the Custis family. He had a well-documented lifelong relationship with the descendants of Martha Washington.
Costin became 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.
In July 1802, the Law family manumitted Will Costin, along with three other enslaved, possibly including his mother. In 1807, the Law family manumitted eight more, including Costin’s wife Delphy.
Through his life he worked for the rights of African Americans in the District. He enabled the freedom of several enslaved people through emancipation and manumission. One of his daughters, Louis Parke Costin opened a school for free Blacks in his home. He also served as school board president for a school for Black citizens that he helped reopen in 1818. In addition, he helped establish the Israel Bethel AME Church, when the Methodist church he attended began segregating services.
He passed away at home in 1842. He was well regarded; as newspapers in Washington D.C. and Baltimore covered the event. The Baltimore Sun stated, “nearly two hundred hacks [carriages] and other vehicles in line, besides a great many people on horseback.”

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.