The 540-foot Knickerbocker Bridge in Boothbay, Maine, is the longest fiber-reinforced bridge ever constructed. Its lightweight hybrid-composite beams, designed by John Hillman of the HC Bridge Company and built by Harbor Technologies, are made of a corrosion-resistant fiber-reinforced polymer shell filled with reinforced concrete. The shell is one third the weight of steel and one tenth the weight of concrete, allowing for quicker construction (it takes just one backhoe to place the beams), and each beam lasts 100 years longer than ordinary concrete and steel, at a similar cost.