Republic Steel Corporation was one of the last major steel firms to use low-phosphorus Adirondack magnetites, operating the Chateaugay Ore & Iron Company from 1939 to 1967. The Chateaugay mine was one of the deepest commercial iron ore mines in the United States, with stopes as much as below the surface. Lyon Mountain's iron ore was considered the best in the industry and was the material of choice for John Roebling and Sons in the construction of the Brooklyn Bridge. In later years, Roebling used Lyon Mountain ore in the construction of the George Washington Bridge and the Golden Gate Bridge.