The U.S. Army Corps of Engineers had dealt with flooding on the Ohio River as interference to navigation long before the American Civil War, and in 1870 adopted a plan for construction of 13 locks and dams between Pittsburgh and Wheeling, and a few years later Congress authorized funding of a new prototype with adjustable gates near Pittsburgh to secure a 6-foot water flow. As the 20th century began, a series of appropriations funded 18 locks and dams, finally finished in 1929. These were built for flood control, and the canals of 9 foot depth between them facilitated transportation of heavy raw materials (including coal and iron ore) and finished goods (including steel). The McMechen Lockmaster Houses on the Ohio River (built in Marshall County in 1911) are among the few that remain (and have been listed on the National Register of Historic Places since 1992).