<Li> Alexandria's residents had lost representation and the right to vote at any level of government . </Li> <P> After a referendum, Alexandria County's citizens petitioned Congress and Virginia to return the area to Virginia . By an act of Congress on July 9, 1846, and with the approval of the Virginia General Assembly, the area south of the Potomac (39 square miles; 101 km2) was returned, or "retroceded," to Virginia effective in 1847 . </P> <P> The retroceded land was then known as Alexandria County, Virginia, and now includes a portion of the independent city of Alexandria and all of Arlington County, the successor to Alexandria County . A large portion of the retroceded land near the river was an estate of George Washington Parke Custis, who had supported the retrocession and helped develop the charter in the Virginia General Assembly for the County of Alexandria, Virginia . The estate (Arlington Plantation) would be passed on to his daughter (the wife of Robert E. Lee), and would eventually become Arlington National Cemetery . </P> <P> A portion of the Washington Aqueduct opened in 1859, providing drinking water to city residents and reducing their dependence on well water . The aqueduct, which was built by the US Army Corps of Engineers, opened for full operation in 1864, using the Potomac River as its source . </P>

When did the capital moved to washington dc