The Irish ancestry that helped to shape US history

As the United States of America celebrates 250 years of independence, the influence of the island of Ireland on the history of the world's most powerful country is being re-examined.

Out of the 45 men who have held the role of president since the USA's foundation, about half of them trace at least one line of their family back to the island.

The USA's first Catholic leader and its most famously Irish-American president - John F Kennedy - had Irish ancestry in every branch of his family tree.

But perhaps less well known is the significant number of presidents whose Protestant ancestors hailed from the north-east of the island - a heritage known here as Ulster-Scots and in America as Scots-Irish.

First among them was President Andrew Jackson, whose Presbyterian parents emigrated from Carrickfergus, County Antrim, just two years before his birth.

He was the first US president born into poverty and was very much a self-made man.

Jackson became a lawyer and a military general before he entered politics and helped to found the Democratic Party.

He was a popular president who cultivated a "man of the people" image by challenging political elitism and championing the common man.

But he was also a divisive figure due to his fierce temper, defiance of Congress, ownership of slaves and treatment of Native Americans.

Recently, Jackson's legacy has been a source of renewed debate.

President Donald Trump is a fan and sparked controversy when he gave Jackson's portrait pride of place in the Oval Office at the start of his second term.

Jackson was one of 16 former US presidents with ancestral links to modern-day Northern Ireland, according to the Irish Family History Centre.

Also on that list are Teddy Roosevelt, Harry Truman and wartime leader Woodrow Wilson.

Jimmy Carter had ancestors from County Antrim, according to the centre's director Fiona Fitzsimons.

She has traced the ancestry of several US presidents and presented a personal family history to Joe Biden in 2016.

Fitzsimons' work included untangling the family ties of Richard Nixon and Gerald Ford, who replaced Nixon in the aftermath of the Watergate scandal.

Unusually, they "both descended from Irish Quaker families" she said, adding it was a departure from the more common Ulster Presbyterian path to the White House.

"The Quakers - their records are absolutely meticulous," she said, explaining it was possible to trace relatives back as far as the 1600s.

Nixon's maternal line stems from County Kildare while Ford had Ulster roots - his great (x5) grandfather John Blackburn III hailed from Loughgall, County Armagh.

In addition, Ford also had relatives from the neighbouring townland of Creenagh and the County Down village of Donaghcloney.

The Bush family produced two US presidents and the Irish side of their dynasty has been traced back to the town of Rathfriland, County Down.

President George HW Bush's fourth great-grandfather, William Holliday, emigrated from Rathfriland to Kentucky more than 200 years ago, according to Fitzsimons.

But for her, of all the Irish-American presidents, Kennedy was the most in touch with his ancestral roots.

"Even before JFK was elected he was in contact with the relatives back in Wexford, he'd already visited them," the genealogist said.

"He obviously had a genuine interest because even as a young man in his 20s he was using his Irish holiday to reconnect with his Irish relatives."

She explained that at the time of his sister's wedding, Kennedy stayed at an Irish castle before driving to Dunganstown to meet his distant cousins.

"The families knew each other...he knew the exact townland address, where to actually rock up."

Kennedy later returned to Dunganstown as president where he had tea and cake with his Irish cousins in front of the world's media.

His four-day Irish tour set the standard for visiting Irish-American presidents.

It was followed in 1984 by Ronald Reagan, who had a pub lounge named after him when he visited his ancestral home in Ballyporeen, County Tipperary.

Barack Obama and Joe Biden - coincidentally both descendants of Irish shoemakers - took separate tours of their ancestral bases during their time in office.

But such presidential "homecomings" already seem outdated, according to Prof Liam Kennedy from the Clinton Institute For American Studies.

He described Biden as the "last of a tribe" at time when the US relationship with Ireland "has become much more tenuous politically".

He argues the "fracturing" of Irish-America - the decline of some of its social networks and once strong organisations - is reflected in its waning influence in the White House.

"We simply do not have the same numbers of Irish Americans moving into senior and important political office that we once did."

In the most recent US census 38.6m people claimed Irish roots but Kennedy said that identity can be "complex and nuanced".

"Their Irishness matters to them, but it doesn't matter to them politically."

Kennedy contends Irish heritage is no longer an important factor in presidential elections because of the disparate, unpredictable views of the diaspora.

"There is no such thing as an Irish voting block in America, there hasn't been since, the 1950s, 1960s, because the Irish became too fully assimilated."

He pointed out Biden was proud of his immigrant ancestry and would "play that Irish liberal card" but added that current attitudes to US immigration vary widely.

"Some Americans, when I interview them, they will very readily say: 'We were immigrants once, we weren't treated well in this country - that makes me very empathetic toward the current immigrants," he explained.

"You'll talk to other Irish Americans and they will say: 'Our ancestors, they came here, they were immigrants but they came the right way, not like these folks today'."

The professor believes there is a growing conservative minority within the community which is "more visible and more vocal".

"I don't think Irish America is disappearing - it is transforming," he said.