District of Columbia retrocession is the act of returning some or all of the land that had been ceded to the federal government of the United States for the purpose of creating its federal district for the new national capital, which was moved from Philadelphia to what was then called the City of Washington in 1800. The land was originally ceded to the federal government by Virginia and Maryland in 1790. After moving through various stages of federal and state approval, the Virginia portion was returned in March 1847.

Thomson Francis Mason was an American lawyer, planter and politician who served as the mayor of Alexandria between 1827 and 1830, and as a justice of the peace for many years and briefly in the months before his death as a judge of the Washington, D.C., criminal court.