OK, this week I'm being lazy and writing about a bridge that you can't run over, but also the oldest bridge I'll be covering - the Aqueduct Bridge, more commonly known as the High Bridge. It crosses the Harlem River between roughly 173rd St. and Amsterdam in Manhattan (in High Bridge Park) and 170th St. and University Ave. in the Bronx.
The High Bridge was built from 1837 to 1848 to carry water into Manhattan along the Croton Aqueduct, originating at a reservoir built on the Croton River in Westchester County all the way to the old reservoirs in Central Park and at 42nd St. between 5th and 6th Avenues, current location of the main branch of the New York Public Library and Bryant Park. The entire bridge is 1,450 feet long and 114 feet clearance above the Harlem River. It was built with 15 stone arches, eight of 80 feet length and seven of 50 feet length. It has had a walkway that was opened in the 1860's, but the walkway was closed in 1960 due partly to disrepair and partly to people throwing rocks off it onto Circle Line boats passing underneath. Brilliant. There are plans to renovate the walkway and reopen it to pedestrians, tentatively in 2011. On the Manhattan side is a water tower built in 1872 to equalize the pressure on the aqueduct. The tower is open to visitors, I believe on weekends in July and August. The walkway and the surrounding area was apparently quite the place to be seen back in the day.
The Old Croton Aqueduct carried water over land in masonry structures by means of gravity, with a drop in elevation of 13 inches every mile. With the construction of the New Croton Aqueduct, and due to security concerns during World War I, the Old Croton Aqueduct ceased operations in 1917. At that time, the Army Corps of Engineers wanted to demolish the bridge to clear the river of its stone pillars for navigation, but preservationists succeeded in keeping the bridge, although the stone arches over the river were replaced in the 1920's by a single steel arch. The stone arches remain over land in the Bronx. Much of the old aqueduct pathway is still a footpath, particularly northward from Van Cortlandt Park in the Bronx.