On November 2, 1825, Willard was chosen architect and superintendent of Bunker Hill Monument, his design having been accepted by the building committee in the following year. Construction began in 1827. Willard discovered satisfactory granite quarries for the stone at Quincy, and the granite for the monument came from there. Willard also invented the machinery to cut and handle the slabs of stone in what became known as the Bunker Hill Quarry, which evolved into a major industry for the town. To get the cut slabs to a wharf on the Neponset River, a distance of two and three-quarters miles, the first commercial railway in the United States was built—the Granite Railway—over which, on the morning of October 7, 1826, the first horse-drawn cars passed, under the direction of a young engineer by the name of Gridley Bryant.