President Biden and first lady Jill Bidenat Windsor Castle on Sunday. But while that gathering was a first for the first couple, the queen's encounters with American presidents and their wives is a piece of history all its own.
In her nearly 70-year reign, Queen Elizabeth may have met more U.S. presidents than anyone else alive today.
Some were a bit out of order. She met the nation's 31st president, Herbert Hoover, at a 1957 luncheon — 24 years after he left office.
And she was only Princess Elizabeth when she and her late husband met President Harry Truman in Washington, on behalf of her father, King George.
But most of the encounters have been as queen, and with a sitting president — including a 1959 visit by Dwight Eisenhower to Balmoral Castle in Scotland, a 1961 state dinner at Buckingham Palace for John and Jackie Kennedy, and a 1969 palace tour for President Richard Nixon.
In 1976, President Ford played host, waltzing with Queen Elizabeth at the White House to celebrate the nation's bicentennial.
Jimmy Carter also made quite an impression on the queen and her mother. During a 1977 Buckingham Palace state dinner — instead of bowing his head or shaking the queen mother's hand, he decided to kiss her right on the lips.
Ronald Reagan, a personal favorite of her majesty, bonded with the queen over their mutual love of horses.
And in 1991, President George H.W. Bush took the royal couple to one of America's favorite pastimes: a baseball game, between the Baltimore Orioles and the Oakland A's.
Bill Clinton and George W. Bush each met with the queen and Prince Philip on numerous occasions, without any major breaches of royal protocol.
Unfortunately, more recent presidents weren't so lucky.
While toasting the monarch at a 2009 state dinner, President Obama kept right on talking as the band played the British national anthem.
And most recently, Donald Trump drew some raised British eyebrows when he walked ahead of the queen during their 2018 visit.
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