PHILADELPHIA — After speeches to Congress and the United Nations, aimed squarely at spurring world leaders toward bold action on immigration and the environment, Pope Francis will embark on the segment of his American journey expected to be the most centered on ordinary Catholics: a Vatican-organized rally for the family that will culminate in an outdoor Mass for a million people.

Francis will spend the last two of his six days in the U.S. in Philadelphia as the star attraction at the World Meeting of Families, a conference for more than 18,000 people from around the world that has been underway as the pope traveled to Washington and New York.

In every city, Francis has been greeted by throngs of cheering, weeping well-wishers, hoping for a glance or a touch from the wildly popular spiritual leader. Philadelphia is expected to be no different. The unprecedented security for the anticipated crowds has been so heavy that organizers of the visit worried people would be scared away.

“He has a magnetic personality that not only appeals to Catholics, but to the universal masses. He’s not scripted. He’s relatable. His heart, in itself, you can see that reflected through his message,” said Filipina Opena, 46, a Catholic from LaMirada, California, as tour groups and families walked among Philadelphia’s historic sites, taking pictures ahead of the pope’s visit. “People feel he’s sincere and he’s genuine. The more people hear him, the more they see him, they all understand and realize it.”

An Argentine on the first U.S. visit of his life, Francis will be given a stage steeped in American history. He will speak at Independence Hall, where the Founding Fathers signed the Declaration of Independence and Constitution, and will do so from a lectern used for the Gettysburg Address, another nod to Abraham Lincoln, one of the four Americans the pope cited as inspirations in his address to Congress.