On the lonely shores past which La Salle and later explorers voyaged have been built villages, towns, and cities. This region is to-day the clearing-house of the commerce of the central plain of North America. From the western terminals of the lake routes railways pass over the plains and mountains of the Northwest to the Pacific; from their eastern ports stretch lines to the seaboard cities of the Atlantic. The farms of the Northwest send yearly one hundred and fifty million bushels of wheat, six hundred million bushels of oats, and a billion bushels of corn to Chicago and Buffalo and thence to the eastern states and Europe. Coming from the west, the transcontinental roads pay tribute at Chicago and then choose between the route north of Lake Erie via Detroit, or south via Cleveland. They unite at Buffalo and follow the Mohawk Valley to the Hudson and then to New York or Boston; or they pass the Alleghanies farther south and reach the coast at Philadelphia, Baltimore, or Norfolk. In any case, by land or water, from the north or from the west, these products come to the Great Lakes, and are carried from their ports to the factories and markets of the East, or to steamers bound for Europe. This combination of land and water transportation makes the Great Lakes the keystone of American industry. We have spoken of the four upper lakes as united commercially into one great sea. Before Lake Superior could be entered from the others one formidable obstacle had to be overcome. Between Lake Superior and Lake Huron was a ledge of rocks half a mile long over which the waters ran in swirling rapids, forming the Sault (or Rapids of) Ste. Marie. At this point the famous “Soo” Canal has been constructed with a single lock which is the largest and costliest in the world, though it will soon be surpassed by those at the entrance of the Panama Canal. This canal was built in 1855, when the presence of iron and copper deposits in Michigan, Wisconsin, and Minnesota was first discovered. To-day the tonnage passing yearly through it runs up into figures that are almost beyond belief; but these figures form the best single index of the traffic of the Great Lakes. In the seven open months of 1907 there passed through the “Soo” one hundred million tons of freight valued at four hundred and fifty million dollars. This tonnage is nine times that of the Suez Canal. The mines whose discovery made necessary the cutting of the “Soo” Canal supply a large part of this freight. Of iron ore alone they send thirty-three million tons to the foundries and furnaces of Pittsburg and other centres, where the raw material is manufactured into articles of iron and steel which form the basis of modern civilized existence. From the deposits of the upper Michigan peninsula comes yearly one-seventh of the world’s supply of copper.