History in its broadest aspect is a record of man's migrations from one environment to another. America is the last great goal of these migrations. He who would understand its history must know its mountains and plains, its climate, its products, and its relation to the sea and to other parts of the world. He must know more than this, however, for he must appreciate how various environments alter man's energy and capacity and give his character a slant in one direction or another. He must also know the paths by which the inhabitants have reached their present homes, for the influence of former environments upon them may be more important than their immediate surroundings. In fact, the history of North America has been perhaps more profoundly influenced by man's inheritance from his past homes than by the physical features of his present home. It is indeed of vast importance that trade can move freely through such natural channels as New York Harbor, the Mohawk Valley, and the Great Lakes. It is equally important that the eastern highlands of the United States are full of the world's finest coal, while the central plains raise some of the world's most lavish crops. Yet it is probably even more important that because of his inheritance from a remote ancestral environment man is energetic, inventive, and long-lived in certain parts of the American continent, while elsewhere he has not the strength and mental vigor to maintain even the degree of civilization to which he seems to have risen. Three streams of migration have mainly determined the history of America. One was an ancient and comparatively insignificant stream from Asia. It brought the Indian to the two great continents which the white man has now practically wrested from him. A second and later stream was the great tide which rolled in from Europe. It is as different from the other as West is from East. Thus far it has not wholly obliterated the native people, for between the southern border of the United States on the one hand, and the northern borders of Argentina, Chile, and Uruguay on the other, the vast proportion of the blood is still Indian. The European tide may in time dominate even this region, but for centuries to come the poor, disinherited Indians will continue to form the bulk of the population. The third stream flowed from Africa and was as different from either of the others as South is from North.