During his first private meeting with Pope Francis in the Vatican two years ago, Cardinal Timothy M. Dolan said, the pope took out an atlas with a map of the United States and asked Cardinal Dolan, the archbishop of New York, to point out the various regions and cities and talk about how they differed.

Francis seemed to recognize that he had some homework to do: When he travels this month to Washington, New York and Philadelphia, the visit will be his first to the United States. Both of his most recent predecessors, Benedict XVI and John Paul II, traveled to the United States before rising to the papacy. Other Catholic prelates from around the world have come for fund-raisers, speaking engagements or global Catholic events, like World Youth Day in Denver in 1993.

But Francis, a former archbishop of Buenos Aires, had steered clear of the United States, which has the world’s fourth-largest Roman Catholic population. Something of a homebody, preferring to hang out with the poor than the rich and powerful, he has waited until 78 to visit the economic giant that likes to think of itself as the center of everything.

“He’s a little nervous about coming,” Cardinal Dolan said at an interfaith event in New York in May. “Not that he lacks any confidence in the reception of friendship that he knows he’ll get, but he readily admits he has never been to the United States.”