The success of miller James H. Gambrill became apparent when he built Edgewood, the grand house on the hill. When it was constructed around 1872, the brick, three-story Second Empire style house was one of the largest single-family residences in Frederick County. With 17 rooms and seven fireplaces, the house was richly finished with Italian marble mantles and features a three-story central hall with a grand staircase. Other sophisticated innovations for the time included a coal-burning furnace, a cooking range, gas lamps, and hot and cold running water. Unfortunately, to avoid financial ruin, Gambrill was forced to sell Edgewood and the mill in 1897.
Today the Gambrill House is home to the administrative headquarters of the National Park Service's Historic Preservation Training Center. Founded in 1977, the center is tasked with developing the craft skills of National Park Service employees who preserve and maintain the thousands of historic structures in the National Park System, including Jefferson Memorial, Abraham Lincoln's Boyhood Home, C&O Canal, Fort McHenry, and the USS Cairo ironclad gunboat .