The falls line was passed long before the colonial period came to an end, and pioneers were working their way from clearing to clearing, up into the mountains, by the early eighteenth century. As they approached the summit of the eastern divide, leaving the falls behind, the essential isolation of the provinces began to weaken under the combined forces of geographic influence and common need. The valley routes of communication which determined the lines of advance run parallel, across the first frontier, but have a tendency to converge among the mountains and to stand on common ground at the summit. Every reader of Francis Parkman knows how in the years from 1745 to 1756 the pioneers of the more aggressive colonies crossed the Alleghanies and meeting on the summit found that there they must make common cause against the French, or recede. The gateways of the West converge where the headwaters of the Tennessee and Cumberland and Ohio approach the Potomac and its neighbors. There the colonists first came to have common associations and common problems. Thus it was that the years in which the frontier line reached the forks of the Ohio were filled with talk of colonial union along the seaboard. The frontier problem was already influencing the life of the East and impelling a closer union than had been known before. The line of the frontier was generally parallel to the coast in 1700. By 1800 it had assumed the form of a wedge, with its apex advancing down the rivers of the Mississippi Valley and its sides sloping backward to north and south. The French war of 1756-1763 saw the apex at the forks of the Ohio. In the seventies it started down the Cumberland as pioneers filled up the valleys of eastern Kentucky and Tennessee. North and south the advance was slower. No other river valleys could aid as did the Ohio, Cumberland, and Tennessee, and population must always follow the line of least resistance. On both sides of the main advance, powerful Indian confederacies contested the ground, opposing the entry of the whites. The centres of Indian strength were along the Lakes and north of the Gulf. Intermediate was the strip of "dark and bloody ground," fought over and hunted over by all, but occupied by none; and inviting white approach through the three valleys that opened it to the Atlantic. The war for independence occurred just as the extreme frontier started down the western rivers. Campaigns inspired by the West and directed by its leaders saw to it that when the independence was achieved the boundary of the United States should not be where England had placed it in 1763, on the summit of the Alleghanies, but at the Mississippi itself, at which the lines of settlement were shortly to arrive. The new nation felt the influence of this frontier in the very negotiations which made it free. The development of its policies and its parties felt the frontier pressure from the start.