President Barack Hussein Obama is the newest member of an exclusive club of 20 U.S. presidents who claim Irish ancestry.

Obama's Irish great-great-great-grandparent, Falmouth Kearney, who left Moneygall in Co. Offaly in 1850, puts him at 13th position in an informal ranking, alongside James Polk and just ahead of Richard Nixon.

Obama is descended from Ohio and Indiana immigrants who came from the borders of Counties Offaly and Tipperary.

Obama is also a member of an even more select group of just four presidents whose fathers were born outside the U.S. And while Obama's father was born in Kenya, the other three presidential fathers were all born in Ireland; the parents of Andrew Jackson and James Buchanan, and the father of Chester Arthur.

Obama has a relatively close link to Falmouth Kearney because his great-grandfather Ralph Waldo Emerson Dunham (Falmouth's grandson) was still alive for part of Obama's childhood. Ralph died in 1970 at the age of 76 when Obama was nine.

Ralph's mother, Mary Anne Kearney Dunham, was Falmouth Kearney's youngest daughter, and she was born in 1869. She was nine when Falmouth died in 1878, almost three years after he had arrived in America on the good ship Marmion.  Both herself and the man she married, Jacob, would later die on the same day in 1936.

However, while much of the spotlight has focused on Obama's direct relatives, the Kearney family has been in the U.S. since the early 1780s. The Kearneys had already started to emigrate despite the fact that the family was still prominent in Shinrone, a more extensive Co. Offaly community eight miles north of Moneygall.

There the family patriarch, 85-year-old Joseph, was presiding over the decline of a small textile and property empire he had set up with his enterprising brother Michael, a successful Dublin wig maker and father of Trinity College Provost and later Protestant Bishop of Ossory, John Kearney.

Joseph's grandson Thomas (c. 1765-1846) was the first to leave Ireland, settling in Baltimore and offering his services as a master carpenter. (It is tempting to speculate that he might even have been engaged in building the White House.)

By 1791 Thomas had married 17-year-old Sarah Baxley of Fairfax County at Baltimore Methodist Church, and within a decade they had taken up a land grant in Ohio, where they settled in Ross County near the site of the future county seat of Chillicothe. There Thomas was joined by his 23-year-old tailor brother John (1782-1870). Their brother William, a Moneygall shoemaker and small-scale tenant farmer, then watched as virtually all his children - Sarah, Thomas, William, Margaret and Francis - emigrated and settled near their uncles in the American Midwest.

In Ohio, Francis Kearney's early efforts at farming were relatively successful so that by the time he died in 1848, he had a sizable holding along the line between Pickaway and Ross Counties.

The Ross County lands, located on the North Fork of Paint Creek, he willed to his 54-year-old brother Joseph, the only one of his generation left in Moneygall.

Joseph had inherited his father William's shoe-making business on the latter's death in 1828, and he and his wife Phoebe were well settled in the small Co. Offaly village. They had four children, ranging in ages from 22 downwards. Margaret, the eldest, was already married to William Cleary, who was more than twice her age.

Her brother Falmouth, named for his maternal grandfather Falmouth Donovan of Ballygurteen, was 18, and the two younger siblings, William and Mary Anne, were 15 and 11, respectively. Within a year, Joseph, his wife and family had made the decision to leave Ireland and by 1851 the two parcels of land that made up the smallholding near Moneygall (still known today as "Kearney's Fields") were put up for public auction by the then landlord, Rev. William Minchin, who lived at nearby Greenhills.

The 63-year-old Protestant rector of Dunkerrin parish was selling his debt-laden estates and moving his family (which numbered 19 in total) lock, stock and barrel to Australia and New Zealand.

Falmouth's Uncle Thomas, who died in 1845 in Wayne Township, Ohio, at the age of 45, has no recorded spouse, but his will refers to a son, Thomas, then living in Ireland, and to a favorite niece with the fateful name of Anna Minchin, indicating a connection with the landlord family.

Meanwhile Falmouth Kearney married a local girl named Charlotte Holloway. The family (which would eventually include nine children) later moved to Tipton County in Indiana, just south of the present-day city of Kokomo, and north of Indianapolis.

Sadly, the story was not all one of hope and joy: Falmouth's siblings, William and Mary Anne, who had come from Ireland as teenagers, died in their 20s in 1855 and 1866 respectively, and his sister Margaret's husband, William Cleary, died in 1862.

By the early 1870s, Falmouth and Charlotte Kearney's eldest daughter Phoebe was attracting the attention of a young man whose family had moved from West Virginia to the Tipton community some years before. He was David Dunham, one of the seven children of Jacob and Louisa Dunham. When he married Phoebe in 1873, they were both 19.

Three years later David Dunham's brother Jeptha married Martha Kearney.

Within two years of Martha's wedding, the Kearney family lost both parents (Charlotte died in 1877 and Falmouth in 1878, while still only in their 40s). Mary Anne was nine and was raised by her older married sisters. This situation resulted in the sealing of the Dunham connection 12 years later with her marriage to a third brother, 29-year-old Jacob, who had already established himself as a druggist.

Jacob and Mary Anne's second son, one of seven siblings, was Ralph Waldo Emerson Dunham Sr., Barack Obama's great-grandfather. Of Ralph's brothers and sisters, all born before 1900, some were still living as late as 1980, and the husband of one died only in 1991.

Ralph Waldo Emerson Dunham's son, Stanley Armour Dunham, and his wife Madelyn Payne "Toot" Dunham became the beloved grandparents who raised Obama from the age of 10.

Stanley's death in 1992 deeply affected Obama, who married his wife Michelle the same year. Just three years later, Barack's mother, Dr. Stanley Ann Dunham, died at the age of 54.

Poignantly, Madelyn would die on November 3, 2008, just one day before her grandson was elected President of the U.S. in a historic landslide election.

Obama, who had earlier left the campaign trail to spend time with the ailing Madelyn, told a crowd of supporters that his Irish-American relative was the source of his family's strength. "She was the cornerstone of our family, and a woman of extraordinary accomplishment, strength, and humility. She was the person who encouraged and allowed us to take chances. She's the one who taught me about hard work."

Note: Genealogical information used in this article is based on preliminary research by Eneclann, Ancestry.com and Roger Kearney of Troy, Ohio (including the latter's transcriptions of tombstone inscriptions and wills), as published on their websites and may be subject to later amendment or revision.