Alexandria County was part of the original 100 square miles (260 km²) square created the District of Columbia in 1791 pursuant to Article I, Section 8, paragraph 17, of the United States Constitution. The portion of the District created from territory ceded by Virginia in Fairfax County was termed Alexandria County of the District of Columbia. It included all of the present Arlington County, Virginia, plus part of what is now the independent city of Alexandria, Virginia. The area was retroceded to Virginia by an act of the United States Congress on July 9, 1846, following a referendum of its citizens.