Alexandria, a N. E. county of Virginia, on the Potomac, opposite Washington; area, 36 sq. m.; pop. in 1870, 16,755, of whom 7,310 were colored. It was once a part of the District of Columbia, and was retroceded to Virginia by act of congress in 1846. Its surface is hilly and its soil is poor and thin. The staple products are corn, wheat, oats, and hay.