The Bass Island Brownstone Company Quarry, also known as the Basswood Island Quarry, on Basswood Island in Lake Superior was operational from 1868 to 1893. The brownstone was first used for construction of the second Milwaukee County Courthouse, now demolished. The quarry, now filled with water, is about 200 feet (61 m) long and about 25 feet (7.6 m) deep. Blocks of sandstone remain, together with the rusting remains of quarrying machinery. All company buildings and workers' cabins have disappeared.