To solve the problem of increasing the span distance, other alternatives to beam and arch bridges included suspension and cantilever bridges.  Cantilever bridges are a modified form of beam bridge, with the support being placed not at the end, but somewhere in the middle of the span. A cantilever is a structure or beam that is unsupported at one end but supported at the other, like diving boards.  This configuration made longer spans possible and wider clearance beneath.  Among the largest cantilever bridges in the United States is the Commodore John Barry Bridge.  The cantilever bridge was a popular type of bridge in the first half of the twentieth century, but at present, some commentators believe that the cable-stayed bridge will replace it for comparable spanning distances.  It has been seen as advantageous due to its ability to span wide spaces and be built without the need of expensive falseworks (used to support the bridge under construction) or foundation piers. 

     The Pulaski Skyway (left), designed by Sigvald Johannesson, connects Jersey City and Newark, New Jersey.  This is the Hackensack River crossing.  As with other major bridge construction, Native Americans participated in the building of this bridge, in particular, members of the Kahnawake Mohawk Tribe.  The bridge was built between 1930 and 1932 and was named "Most Beautiful Steel Structure" for 1932 by the American Institute of Steel Construction.  It was originally known as the Diagonal Highway. 
    
     To the right is the Royal Alexandra Bridge (1901), also known originally as the Interprovincial Bridge, this is a cantilever bridge linking Hull (Quebec) with Ottawa (Ontario) across the Ottawa River.  The bridge took nearly a decade to complete after the groundbreaking in 1892.  At the time of completion the main cantilever span of 556 feet was the longest in Canada, and fourth longest in the world, according to the Transport Canada site.  Its total length is 1,848 feet, and its tower posts are 95 feet high.  It was designed to handle both rail and vehicular traffic, as well as pedestrians.  The images highlight the symmetry of this beautiful bridge.  

      For websites discussing cantilever bridges, see, e.g., Acrow Bridges and Teachersdomain.org.



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