The Leonard P. Zakim (/ˈzeɪkəm/) Bunker Hill Memorial Bridge (or Zakim Bridge) is a cable-stayed bridge across the Charles River in Boston, Massachusetts. It is a replacement for the Charlestown High Bridge, an older truss bridge constructed in the 1950s. Of ten lanes, using the harp-style system of nearly-parallel cable layout, coupled with the use of “cradles” through each pylon for the cables, the main portion of the Zakim Bridge carries four lanes each way (northbound and southbound) of the Interstate 93 and U.S. Route 1 concurrency between the Thomas P. “Tip” O’Neill Jr. Tunnel and the elevated highway to the north. Two additional lanes are cantilevered outside the cables, which carry northbound traffic from the Sumner Tunnel and North End on-ramp. These lanes merge with the main highway north of the bridge. I-93 heads toward New Hampshire as the “Northern Expressway”, and US 1 splits from the Interstate and travels northeast toward Massachusetts’ North Shore communities, crossing the Mystic River via the Tobin Bridge.
The bridge and connecting tunnel were built as part of the Big Dig, the largest highway construction project in the United States. The northbound lanes were finished in March 2003, and the southbound lanes in December. The bridge’s unique styling quickly became an icon for Boston, often featured in the backdrop of national news channels, to establish location, and included on tourist souvenirs. The bridge is commonly referred to as the “Zakim Bridge” or “Bunker Hill Bridge” by residents of nearby Charlestown.
The Leverett Circle Connector Bridge was constructed in conjunction with the Zakim Bridge, allowing some traffic to bypass it.