New York & Mahopac Railroad, Bridge L-158, Schoolhouse Road, Goldens Bridge, Westchester County, NY

Significance: The development of the metal truss bridge in America largely paralleled the needs of the railroads, and the through-truss double-intersection form patented by Squire Whipple in 1846 and modified by John W. Murphey in 1863 was one of the most popular, playing a major part in railroad bridge building between 1860 and 1885. The form evolved out of the economic and technological necessity of retaining the small panel size, yet increasing the depth (and thereby increasing the strength) of the truss. As the most efficient angle for a diagonal member was 45 degrees, it followed that the height of the truss increased, so the number of panels that the diagonal needed to cross would increase. Bridge L-158 is an excellent example of the double-intersection form at the height of its popularity.
Survey number: HAER NY-148
Building/structure dates: 1883 Initial Construction
Building/structure dates: 1904