The history of the United States, according to newer views which have largely supplanted, or progressed beyond, those of the New England school of great historians, is the history of the march of a civilization, chiefly English, across the vast North American continent, within the short period of three hundred years. It is the story of the transformation of a wide-stretching wilderness-of an ever-advancing frontier-into great cities, diversified industries, varying social interests, and an intensely complex life. Wave upon wave of races of mankind has flowed over the developing and enlarging West, and each has left its impress on that area. Across the trail of the Indian and the trapper, the highway of the pioneer on his westward journey, have spread the tilled fields of the farmer, or along it has run the railroad. The farm has become a town-site and then a manufacturing city; the trading post at St. Paul and the village by the Falls of St. Anthony have expanded into the Twin Cities of the Northwest; the marshy prairie by the side of Lake Michigan, where the Indians fought around old Fort Dearborn, has come to be one of the world's mighty centers of urban population-and all this transformation within the memory of men now living.