The following is a brief account of where the Scotch-Irish started out from, travelled to, and then settled in, America.
Source: "The Scotch-Irish: A Social History"..by James G Leyburn.
Ulster, one of the four traditional kingdoms of Ireland, was only 20 miles across the channel from Scotland. In 1603, a laird of northern Ayrshire (Scotland), Hugh Montgomery, learned that Con O'Niell was in prison. O'Niell was a chieftain of large properties in County Down, and County Antrim. Montgomery proposed to O'Neill a bargain. He could effect the escape and pardon of O'Neill, if in return, O'Neill would grant him half of his lands.
In 1609, the two Scots, Montgomery and Hamilton, began to induce tenants and other Scots, to come over as farmer-settlers. Within 10 years, the population of the Plantation of Ulster, had reached around eight thousand. The assignment of lands to Scottish undertakers, was to have a permanent effect on the character of Ulster. Despite every vicissitude, including massacres and war, the Plantation gradually grew strong and proved to be a success. If one cause more than any other can be singled out for its success, it would be the presence, the persistence, and the industry of the Scots in the region.
Back in Scotland, there was an increasing hardship occasioned by the spread of a form of land tenure, called the feu, which had the effect of dispossessing many farmers of their traditional lands. They were attracted to the generous lands visible across the channel from the shores of south western Scotland. Any Scot who had the inclination might now take the short journey across to Ulster and there, on easy terms, acquire a holding of land reputed to be far more fertile and productive than any he was likely to know in his own country.
From 1634 onward to 1690, life for the colonists of Ulster was to consist of a series of crises, some of them so prolonged and severe that the very existence of the Scottish settlements were threatened. The trouble had two causes: religious ex-actions from England and native uprisings. Under the Jesuits the Irish people had become fervently Catholic; to them the Protestants of Ulster were heretics as well as interlopers. The native Irish resented the intrusion of Scottish (and English) settlers on their ancestral lands, and their resentment exploded in 1641 in bitter insurrection.
Between 1717 and the Revolutionary War some quarter of a million Ulstermen came to America.
The first migration, then was touched off by a combination of drought, rack-renting, diminished trade in woolen goods, depression, and also religious discrimination and persecution. When the fourth successive year of drought ruined the crops in 1717, serious preparations began to be made for a migration.
Ships were chartered, consultations were held, groups were organized, and property was sold. More than five thousand Ulstermen that year made the journey to the American colonies. There were but two real drawbacks--the dangers of an ocean crossing (especially for woman and children) and the expense of that passage. The practice of indenture has long been a familiar device.
There were five great waves of emigration, with a lesser flow in intervening years: 1717-1718, 1725-1729, 1740-1741, 1754-1755,
In 1717, at least 5000 Ulstermen left Ireland. Jonathan Dickinson reported from Philadelphia in 1717, that there had arrived from ye north of Ireland many hundreds in about four months, and that during the summer we have had 12 or 13 sailings of ships from the North of Ireland with a swarm of people.
The second wave was so large, that not only the friends of Ireland, but even the English Parliament became concerned. In the Pennsylvania Gazette it was reported that poverty, wretchedness, misery and want are become almost universal among them; that...there is not corn enough raised for their subsistence one year with another; and at the same time the trade and manufactures of the nation being cramped and discouraged, the labouring people have little to do, and consequently are not able to purchase bread at its present dear rate; that the taxed are nevertheless exceeding heavy, and money very scarce; and add to all this, that their griping, avaricious landlords exercise over them the most merciless racking tyranny and oppression. Hence it is that such swarms of them are driven over into America.
The third wave marked, on the American side, the first movement of Scotch-Irish in any numbers beyond the confines of generous Pennsylvania to the southwest. Following the path through the Great Valley, many Ulstermen now went into the rich Shenandoah Valley of Virginia, whose southern extremity opened out toward North and South Carolina. The second wave had so well established the Scotch-Irish in the south eastern tier of counties in Pennsylvania, that their influence, even in political affairs in the Quaker commonwealth was becoming impressive. Famine struck Ireland in 1740, and was certainly the principal occasion for the third large wave, which included numbers of substantial Ulstermen.
The fourth exodus had two major causes: effective propaganda from America, and calamitous drought in Ulster. A succession of governors of North Carolina had made a special effort to attract to that province colonists from Ulster and from Scotland. Governor Dobbs of North Carolina, (formally from Carrickfergus County Antrim) declared that as many as ten thousand immigrants had landed in Philadelphia in a single season, so that many were obliged to remove to the southward for want of lands to take up in Pennsylvania.