In 1790, Congress authorized the establishment of a territory 10 miles square on the Potomac River as the Capital of the United States, following President Washington's recommendation to use land on both sides of the river. Surveyor Andrew Ellicott, notified in 1791 by Secretary of State Thomas Jefferson to designate the federal boundary, hired astronomer Benjamin Banneker, a free black man. Together they established the locations of 40 sandstone markers set at one-mile intervals on land ceded by Maryland and Virginia for the nation's capital. Virginia reclaimed her lands in 1846. The stone in this park, set in 1792 during the Maryland Boundary Survey, is Northwest Number 6, marking a point six miles north of the West Corner Stone. The Boundary Stones are considered the first monuments erected by the United States.