Work on an aqueduct across the Potomac River and a canal down to Alexandria began in 1831 and was finished in 1843. Georgetown merchants and Congress both opposed what they saw as a diversion of commerce and profits to the Alexandrians, but the continuous waterway, elevated above the Potomac's surface, became the primary route of traffic and outlet, with Rock Creek Basin falling into disuse.
The Potomac Aqueduct was put under federal control during the Civil War, when it was decked over and used for foot and draft traffic. In 1886, it was taken over again by federal authorities and fitted to be a steel deck truss bridge. Eventually this avenue across the Potomac was replaced by the Key Bridge, which opened in 1923.