Joe Biden shook hands and greeted well-wishers as he toured Co Louth as he continues his visit to the Republic of Ireland.
The US president and his motorcade stopped off in Dundalk on Wednesday evening, with Mr Biden greeted with shouts of “Welcome home Joe” and waving American flags.
Earlier, locals had turned out in numbers on motorway overpasses as well as lining road sides approaching Carlingford despite heavy rain in an area Mr Biden has traced ancestral roots to.
While there, he was met by Ireland’s deputy premier (Tanaiste) Micheal Martin, and the pair toured Carlingford Castle together.
The castle offers a view of Carlingford Lough where Mr Biden’s great-great grandfather Owen Finnegan left via Newry port during the Irish famine in 1849 for a new life in the United States.
As Mr Biden walked around the castle amid the rain, someone shouted up to ask him what he thought of the weather, to which the president quipped: “It’s fine, it’s Ireland.”
In Dundalk, members of the public in ponchos and raincoats had been waiting to greet the US president with a sign reading “Dundalk welcomes President Biden” hung above Clanbrassil Street.
Mr Biden went into McAteers The Food House restaurant on the same street shortly before 7.15pm, where he chatted with staff.
Former Irish rugby player Rob Kearney was among those accompanying Mr Biden as he stopped off in the town.
The US president arrived in the Republic of Ireland earlier on Air Force One where he was greeted on the tarmac at Dublin Airport by Taoiseach Leo Varadkar.
On Wednesday morning, Mr Biden met with UK Prime Minister Rishi Sunak in Belfast, where the pair spoke about the “incredible economic opportunities” for Northern Ireland.
The Prime Minister described the UK’s relationship with the US as being “in great shape”, describing them as “very close partners and allies”.
The Republic of Ireland leg of the president’s four-day tour of the island will see him travel to the Irish capital, Co Louth and Co Mayo.
Mr Biden became the sixth person to travel through Dublin Airport while serving as US president, following Barack Obama’s visit to the country in May 2011.
Ireland’s Ambassador to the US Geraldine Byrne Nason was also among the politicians and officials to greet the president, alongside her US counterpart Claire D Cronin and her husband Ray.
He is also expected to deliver a number of speeches over the course of his three days in the country, – including in Dublin, at St Muredach’s Cathedral in Ballina and to the Irish Parliament.
Mr Biden is due to meet Irish President Michael D Higgins on Thursday, followed by a further meeting with Mr Varadkar, whom he recently hosted for St Patrick’s Day.
The White House said Mr Biden will take part in a tree-planting ceremony and the ringing of the Peace Bell at the President’s official residence, Aras an Uachtarain.
He will tour the Sanctuary of Our Lady of Knock and visit the North Mayo Heritage and Genealogical Centre’s family history research unit.
Earlier on Wednesday, the White House denied Mr Biden was “anti-British”, with Amanda Sloat, senior director for Europe at the US National Security Council, saying: “It’s simply untrue.”
“The fact that the president is going to be engaging for the third time in three months, and then again next month and then again in June, with the Prime Minister of the UK shows how close our co-operation is with the UK,” she added.