Celebrate St. Patrick’s Day with the invisible Irish, the Scotch-Irish. These are Scots who moved to Ireland four centuries ago, their offspring later immigrating to this country during the colonial period.

Once on these shores, the Scotch-Irish all but disappeared as a distinct group, dispersing and intermixing with other immigrant groups as they pushed westward and southward to the frontier.

Conversely, the Irish Catholic immigration was later, larger and more focused in urban areas, allowing them to retain a more distinct identity as Irish-Americans. But given that the American population was 15 percent Scotch-Irish at the time of the Revolution, there’s a good chance you may be a bit Scotch-Irish — and not even know it.

If so, you come from good hearty stock, although the Scotch-Irish were stubbornly independent, even cantankerous — exactly the raw material George Washington wanted for his army. A Hessian officer even styled the American Revolution as “nothing more or less than a Scotch-Irish Presbyterian rebellion,” while Washington himself said, “If defeated everywhere else, I will make my last stand for liberty among the Scotch-Irish of my native Virginia.”

The Scotch-Irish of North Carolina passed “Resolutions of Independence” in 1775, a full year before the Declaration of Independence. And even our national declaration of July 4, 1776, was handwritten by Charles Thompson, printed by John Dunlap and given its first public reading by John Nixon, all three being Scotch-Irish. Subsequent American presidents with Scotch-Irish ancestry included Andrew Jackson, Ulysses S. Grant and eight others with Ulster roots. Davy Crockett, Stonewall Jackson, Horace Greeley, Stephen Foster and thousands of other Scotch-Irish attained prominence in diverse areas of our national development.

What drove the Scotch-Irish to our raw, risky and unsettled lands in the 1700s? Simply said, they had nothing in Ireland and hoped for everything in America. Virtually all were peasant tenants who worked but did not own the land. So they saw unbounded opportunity in America, a magnet that still draws immigrants to these shores.

It was said that coming to America meant “a greater chance to exercise ambition” for the Scotch-Irish, many of whom were joining friends and family, as rural “townlands” of northern Ireland were virtually transplanted to the American frontier. My family was part of such a migration stream, from the Markethill area of County Armagh, Ireland, to Washington County in western Pennsylvania. They came with neighbors who had distinctive Scottish names such as Acheson, Burns, Campbell, Marshall, McGill, Wilson and dozens more. Letters back home, reporting on available land and religious freedom, triggered new waves of immigration.

Their stories typify American enterprise. Alexander Burns, a Revolutionary War soldier, escaped the British twice and the Indians once before homesteading in Washington County, Pennsylvania. His neighbors in Ireland, the Achesons, became merchants, military officers and legislators. The Campbells came over and started one of the first churches founded on American soil, the Disciples of Christ, which boasted several million members within 50 years and was the church in which both Lyndon Johnson and Ronald Reagan were raised. The Achesons and Campbells carried over Burns family letters in the 1790s and early 1800s, news knitting neighbors together first in Ireland and then again in America.

A quintessentially American story is that of young David Acheson arriving in America from Markethill, virtually penniless, in 1788, and making his way out to the wilds of western Pennsylvania to join his brother. He was 18 years old. But less than 10 years later, David was the Washington County representative in the Pennsylvania Legislature. Philadelphia was then the seat of both the state and national government; per the invitation David received to have dinner in February 1797 with another politician named Washington: “Mr. Acheson is requested to dine with the President on Thursday at four o’clock precisely.”

Years later, in the twilight of his life, 70-year-old David Acheson journeyed back to Ireland and met Lord Gosford, son of his family’s landlord when they had been peasant farmers there. Writing home to his own son, David Acheson said: “Here aristocracy reigns and governs in the pride and pomp of birth and wealth. To me, (from) a country where merit only entitles to favor and reward, the contrast is striking — and in favor of the United States.”

On this St. Patrick’s Day, America remains a meritocracy, as well as the land of the free and the home of the brave, qualities well worth celebrating.

James F. Burns is a professor emeritus at the University of Florida.