Intracoastal Waterway, c.3,000 mi (4,827 km) long, partly natural, partly artificial, providing sheltered passage for commercial and leisure boats along the U.S. Atlantic coast from Boston, Mass. to Key West, S Fla., and along the Gulf of Mexico coast from Apalachee Bay, NW Fla., to Brownsville, Tex., on the Rio Grande. The toll-free waterway, authorized by Congress in 1919, is maintained by the Army Corps of Engineers at a minimum depth of 12 ft (4 m) for most of its length; some parts have 7-ft (2.1-m) and 9-ft (2.7-m) minimum depths. Among some of the waterway's most often used canals along the Atlantic route are the Chesapeake & Delaware and the Chesapeake & Albemarle; along the Gulf route the most used are the New Orleans–Rigolets Cut, the Port Arthur–Corpus Christi Channel, and the Inner Harbor Navigational Canal at New Orleans. The separate Okeechobee Waterway, S Fla., crosses the Florida peninsula. Plans to build a canal across N Florida to link the Atlantic and Gulf sections were blocked in 1971 by a presidential order to prevent potential environmental damage. Many miles of navigable waterways connect with the coastal system, including the Hudson River–New York State Canal System, the Chesapeake Bay, the sounds of North Carolina, the Savannah River, the Apalachicola River, and the entire Mississippi River system. The Intracoastal Waterway has a good deal of commercial activity; barges haul petroleum, petroleum products, foodstuffs, building materials, and manufactured goods.