Boundary Markers of the Original District of Columbia
The Boundary Markers of the Original District of Columbia are the 40 milestones that marked the four lines forming the boundaries between the states of Maryland and Virginia and the square of 100 square miles (259 km²) of federal territory that became the District of Columbia in 1801 (see History of Washington, D.C.#Founding). A survey team led by Major Andrew Ellicott placed these markers in 1791 and 1792; among Ellicott's assistants were his brothers Joseph and Benjamin Ellicott , Isaac Roberdeau, George Fenwick, Isaac Briggs and astronomer Benjamin Banneker. Today, 36 of the original marker stones survive as the oldest federally placed monuments in the United States. Due to the return of the portion of the District south and west of the Potomac River to Virginia in 1846, some of these markers are now within Virginia.
The District of Columbia (initially, the Territory of Columbia) was originally specified to be a square 100 square miles (260 km2) in area, with the axes between the corners of the square running north-south and east-west, and having its southern corner at the southern tip of Jones Point in Alexandria, Virginia, at the confluence of the Potomac River and Hunting Creek (later the site of the Jones Point Lighthouse). The sides of the square are each 10 miles (16 km) long. The specified orientation results in a diamond shape for the District's original boundaries on most maps.
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