Leffert L. Buck (1837-1909) was an American civil engineer and a pioneer in the use of steel arch bridge structures. His projects included the steel suspension bridge over the Niagara Gorge and two of New York City's most notable landmarks: the Brooklyn Bridge (with John Augustus Roebling and Washington Roebling) and the Williamsburg Bridge (with Henry Hornbostel ). The latter, at 1,600 feet, was the longest bridge in the world at the time and a key factor in opening Brooklyn up as a working class neighborhood for Manhattan.