THE Ulster Presbyterians, or "Scotch-Irish," to whom history has ascribed the dominant rôle among the pioneer folk of the Old Southwest, began their migrations to America in the latter years of the seventeenth century. It is not known with certainty precisely when or where the first immigrants of their race arrived in this country, but soon after 1680 they were to be found in several of the colonies. It was not long, indeed, before they were entering in numbers at the port of Philadelphia and were making Pennsylvania the chief center of their activities in the New World. By 1726 they had established settlements in several counties behind Philadelphia.