In the United States the possible development of canals has been neglected and, to a certain extent, stifled by railway building. The Erie Canal, built before the advent of the railway, connects Lake Erie with tide-water at Albany, a distance of 387 miles. For many years it was the chief means of traffic between the Mississippi Valley and the Atlantic seaboard, and although paralleled by the six tracks of a great railway system, it is still an important factor in the carriage of grain and certain classes of slow freight.[9] The level way that made the canal possible is largely responsible for the decline of its importance, for the absence of steep grades enables a powerful locomotive to haul so many cars that the quick transit more than overbalances a very low ton rate by the canal. The Chesapeake and Ohio Canal, designed to connect the Mississippi Valley with the Atlantic seaboard, fared much worse than the Erie Canal. Less than two hundred miles have been completed, and practically no work except that of repair has been done since 1850; the heavy grades between Cumberland and Pittsburg render its completion improbable. An excellent system of canals, the Ohio and Erie and the Miami and Erie, connect the Ohio River with Lake Erie. These canals are in the State of Ohio and aggregate about six hundred miles in length. They are important as coal and ore carriers. Several hundred miles of canals were built along the river-valleys of eastern Pennsylvania before 1840 for carrying coal to tide-water. Most of them have been abandoned; one, the Delaware & Hudson Canal Co., survives as a railway. Inasmuch as the coal went on a down grade from the mines to the markets, it could be carried more economically by railway than by canal. Of far greater importance are the St. Marys Canal on the Canadian side, and the St. Marys Falls Canal on the American side, of St. Marys River. These canals obviate the falls in St. Marys River and form the commercial outlet of Lake Superior. The tonnage of goods, mainly iron ore and coal, is about one-half greater than that of the Suez Canal. About twenty-five thousand vessels pass through these canals yearly. The Chicago Ship and Sanitary Canal,[10] from Lake Michigan to Lockport, on the Illinois River, was designed mainly to carry the sewage of Chicago which, prior to the construction of the canal, was poured into the lake through the Chicago River. The completion of the canal turned the course of the river and caused the water to flow out of the lake, carrying the city's sewage. It is intended to complete a navigable water-way from Chicago to St. Louis deep enough for vessels drawing fourteen feet. Its value is therefore strategic as well as industrial, for by means of it gun-boats may readily pass from the Gulf of Mexico to the Great Lakes.