Joe Biden becomes the 14th U.S. president to meet a pope.
The first was Woodrow Wilson in 1919, who met with Pope Benedict XV in Rome, before the Vatican was a sovereign state.
40 years later, Dwight Eisenhower traveled to Vatican City to meet with Pope John XXIII.
Their meeting was followed by John F. Kennedy's trip to Rome only four years later, where he was welcomed by Pope Paul VI as the first Catholic U.S. president.
BARBARA PERRY
Miller Center, University of Virginia
'It was unclear until President Kennedy's victory in 1960 whether a Roman Catholic could win the presidency in this country because there still was a lot of prejudice against Roman Catholics despite the fact that they constituted and still do 25% of the population.'
In 1965, Pope Paul VI traveled to the United States and met with Lyndon B. Johnson in New York's Waldorf Astoria hotel.
Pope John Paul II was the first pope to visit the White House, where he met with Jimmy Carter, ushering in a new era of deepened relations between the papacy and the U.S. presidency.
BARBARA PERRY
Miller Center, University of Virginia
'Particularly since the Jimmy Carter era in this country since the 1970s and the 1980s when the so-called Moral Majority in this country, which was a born-again protestant religious and political movement, came on the scene, it's been important for presidents to indicate their religiosity and their spirituality if they have it, and being associated with the most visible and the most famous spiritual leader in the world can't hurt.'
Throughout his pontificate, Pope John Paul II held 15 meetings with U.S. presidents. Bill Clinton, George Bush Sr., and George W. Bush were all present at his funeral.
Pope Benedict XVI visited the White House on his 81st birthday in 2008.
In 2009, Barack Obama visited the Vatican for the first time.
-'Your Holiness, thank you very much. It is a great honor for me.'
He returned again as president in 2014 to meet with Pope Francis, who returned the visit just over a year later by coming to the United States.
Donald Trump met with Pope Francis once during his presidency in 2017. The meeting proceeded amicably despite prior public disagreements on climate change and immigration.
The meeting is Joe Biden's fourth with Pope Francis, and the first since he was inaugurated president.
BARBARA PERRY
Miller Center, University of Virginia
'Until Joe Biden, we had another 5-6 decades without another Catholic at the top of the ticket or certainly without a Catholic at the top of the ticket or certainly without a Catholic having won the presidency. So, it's historic to have Joe Biden as the second Roman Catholic to be president of the United States.'
Now, for only the second time in history, a pope welcomes a Catholic U.S. president to the Vatican.
JM
