The Francis Scott Key Bridge, more commonly known as the Key Bridge, is a six-lane reinforced concrete arch bridge conveying U.S. Route 29 traffic across the Potomac River between the Rosslyn neighborhood of Arlington County, Virginia, and the Georgetown neighborhood of Washington, D.C. Completed in 1923, it is Washington's oldest surviving bridge across the Potomac River.Key Bridge was added to the National Register of Historic Places in 1996.