The meeting between Pope Francis and President Obama at the White House continues a tradition going back nearly a century between U.S. presidents and the head of the Roman Catholic Church.

The talks are private, often personal and, always, they take place against the backdrop of the politics of the time. That was the case at the very first such meeting, at the Vatican, as Europe was recovering from World War I.

In January of 1919, President Woodrow Wilson was on a tour of Europe that lasted more than six months. The main purpose of the trip was the Paris Peace Conference, but Wilson's itinerary included Italy, as well.