"Westward lay the march of American Empire. Within thirty years of the establishment of the Union nine new states had been formed in the Mississippi valley, and two in the borders of New England. As early as 1769 men like Daniel Boone had pushed their way into the Kentucky country, skirmishing with the Indians. But the main movement over the mountains began during the War of Independence. The migration of the eighteenth century took two directions: the advance westward towards the Ohio, with its settlement of Kentucky and Tennessee, and the occupation of the north-west forest regions, the fur-traders’ domain, beyond Lake Erie."