The first meeting between a U.S. president and a pope took place on January 4, 1919, when President Woodrow Wilson met Pope Benedict XV at the Vatican. Since then, six popes have met twelve presidents, sometimes more than once.
Some important moments include President John F. Kennedy's meeting with Pope Paul VI, which was the only meeting between a Roman Catholic president and a reigning pope.
The first time a pope visited the White House was in 1979, when President Jimmy Carter hosted Pope John Paul II in Washington D.C.
Now, President Obama has met Pope Francis for the first time at the Vatican, with an agenda focused on the pair's "shared commitment to fighting poverty and growing inequality."
See photos from the first official meetings between presidents and popes here:
President Barack Obama & Pope Francis -- March 27, 2014
President Barack Obama & Pope Benedict XVI -- July 10, 2009
President George W. Bush & Pope Benedict XVI -- June 9, 2007
President George W. Bush & Pope John Paul II -- July 23, 2001
President Bill Clinton & Pope John Paul II -- August 12, 1993
President George H.W. Bush & Pope John Paul II -- May 27, 1989
President Ronald Reagan & Pope John Paul II -- May 2, 1984
President Jimmy Carter & Pope John Paul II -- October 6, 1979
President Gerald Ford & Pope Paul VI -- June 3, 1975
President Richard Nixon & Pope Paul VI -- March 2, 1969
President Lyndon B. Johnson & Pope Paul VI -- October 4, 1965
President John F. Kennedy & Pope Paul VI -- July 2, 1963
President Dwight D. Eisenhower & Pope John XXIII -- December 6, 1959
President Woodrow Wilson & Pope Benedict XV -- January 4, 1919