Despite the fact that Scottish Presbyterians strongly supported the Williamites in the Williamite war in Ireland in the 1690s, they were excluded from power in the postwar settlement by the Anglican Protestant Ascendancy. During the 18th century, rising Scots resentment over religious, political and economic issues fueled their emigration to the American colonies, beginning in 1717 and continuing up to the 1770s. Scots-Irish from Ulster and Scotland, and British from the borders region comprised the most numerous group of immigrants from Great Britain and Ireland to the colonies in the years before the American Revolution. An estimated 150,000 left northern Ireland. They settled first mostly in Pennsylvania and western Virginia, from where they moved southwest into the backcountry of upland territories in the South, the Ozarks and the Appalachian Mountains.