The Manhattan Bridge is a suspension bridge crossing the East River in New York City, connecting Lower Manhattan at Canal Street with Downtown Brooklyn at Flatbush Avenue Extension. Opened to traffic on December 31, 1909, it was the last of the three suspension bridges built across the lower East River, following the Brooklyn and Williamsburg bridges. The bridge was designed by Leon Moisseiff and is recognized for its innovative application of the deflection theory for suspension bridges, which allowed for a more slender and lighter design. It carries seven lanes of vehicular traffic on its upper level, with four tracks of the New York City Subway (B, D, N, and Q trains) on the lower level, along with a pedestrian walkway and a separate bikeway. The bridge's total length is 6,855 feet (2,089 meters), with a main span of 1,470 feet (448 meters). Its distinctive granite and limestone towers are adorned with colonnades and sculptural groups designed by Carl Augustus Heber, symbolizing the settlement of New York City. The Manhattan Bridge is a designated National Historic Civil Engineering Landmark and is a crucial component of the city's infrastructure, handling substantial daily commuter traffic.