Tánaiste and Minister for Foreign Affairs Simon Harris has opened the new Irish embassy in Washington.
The offices, on Pennsyvania Avenue, are next to the White House.
"We begin to write the next chapter in the great story of Ireland-US relations," Mr Harris said.
He described the move as "the culmination of a nearly four-year project to realise a significant commitment of the Global Ireland Strategy and National Development Plan.
"This will be an excellent base from which to grow our vital political, economic and cultural ties with the US over the years ahead," Mr Harris added.
The opening was welcomed in a letter by US President Donald Trump.
"As you celebrate the grand opening of Ireland's new Embassy location, I look forward to continuing to work closely with your country to strengthen our time-honored relationship – especially by advancing fair trade policies and investment opportunities that benefit both of our nations’ citizens," he wrote.
Responding, Mr Harris said: "President Trump is right to draw attention to not just the depth and breadth of our trade and investment ties, but also the potential for these to become yet stronger over the years ahead, in the interests of people throughout the United States and Ireland.
"Today, I am launching an economic impact report which maps Ireland’s economic footprint right across the US and shows the remarkable impact of our partnership in terms of trade, employment, research, tourism and investment.
"Ireland is now the 5th largest source of foreign direct investment in America and Irish companies have created more than 200,000 American jobs.
"This is a superb foundation to build upon over the years ahead and I am looking forward to publishing a new strategy early in 2026 which will chart that way forward," he said.
This will coincide with the 250th anniversary of the signing of the Declaration of Independence on 4 July 1776.
Mr Harris said that three of the signatories were born on the island of Ireland.
US Secretary of Commerce meeting
Tánaiste Simon Harris also met with United States Secretary of Commerce Howard Lutnick in Washington.
During the meeting the economic, trade and investment relationship between Ireland and the US was discussed.
The implementation of the EU-US Framework on an Agreement on Reciprocal, Fair and Balanced Trade, which was agreed in July, was also on the agenda.
Discussions were held on the potential of expanding the list of goods that are exempt from the baseline 15% tariff rate.
Ireland has a particular interest in this as it relates to the spirits and medtec sectors.
The issue of non-tariff barriers, as well as the ongoing Section 232 investigations on pharmaceuticals and semiconductors, was part of today's talks.
The Tánaiste raised the recent proposal by the US to raise the cost of H1B visas applications, and noted the importance of pathways for high-skilled workers, innovators and job creators to live and work in the US.
Mr Harris updated the Secretary on the economic impact report - Ireland and the USA: a shared economic story - which he launched today. The report shows the impact of Irish companies investing across all 50 states.
Additional reporting: Joe Mag Raollaigh, PA
