The Queen has made a joke about US President George Bush's gaffe in which he nearly aged her by 200 years.
The Queen attended a dinner at the British ambassador's residence
In a speech at a dinner in the US, she said: "Mr President, I wondered whether I should start this toast saying I was here in 1776 but I don't think I will."
She was commenting on the president having nearly referred to one of her previous visits being in 1776 not 1976.
The Queen thanked the US for helping to bring peace to Northern Ireland, as she completed her six-day state visit.
The Queen, accompanied by the Duke of Edinburgh, has now left the US and is heading back to Britain.
Mr Bush slipped up earlier in the week as he welcomed the Queen to the US when he began to say that her last previous visit to the US, during the country's bicentenary, had been in 1776.
Realising his mistake he winked at the monarch, saying: "She gave me a look that only a mother could give a child."
The Queen's comment at a dinner at the British ambassador's residence, on the final day of her US tour, raised laughter from the guests.
On a more serious note, she went on to thank Mr Bush and his predecessors for their contribution to the Northern Ireland peace process.
She said: "I would like to take the opportunity, on the day that has seen the formal transfer of power to the devolved Northern Ireland government, to thank you and your predecessors for your contribution to bringing peace in Northern Ireland."
President Bush said the transfer of power in Northern Ireland showed democracy had the power to unite a divided state.
"The people of Northern Ireland took control of their future when Catholics and Protestants came together to form a new government that offers the prospect of peace and reconciliation after years of violence and division."
Earlier the Queen and Prince Philip visited the World War II National Memorial, in Washington DC, and Nasa space centre.
At the memorial they were joined by former US President George Bush senior and his wife Barbara.
The Queen and Prince Philip together placed a wreath in memory of fallen servicemen.
The tour of the eastern US has included visits to the Kentucky Derby horse race and the site of the first permanent English settlement in the US - Jamestown in Virginia - to mark its 400th anniversary.
Following the Queen's return to the UK her carbon footprint will be calculated and offset for the first time for a state visit.
Buckingham Palace will make a donation to an environmental charity to offset the plane journeys made by the royal party.
THE QUEEN'S FIRST CARBON-OFFSET STATE VISIT
Total air miles
- 13,317 km or 8,275 milesAmount of CO2 emitted based on scheduled flights
- 1. 5 tonnesEstimated offset cost per person
- £13.20 to £14.18 ($26.22-$28.17) depending on type of offset package
Source: The Carbon Neutral Company carbon calculator