Schedule of events for Pope Francis' U.S. visit
Earlier Sunday morning, the pope addressed a gathering of bishops at the Saint Charles Borromeo Seminary.
Before his speech, the Holy Father visited with five victims of sexual abuse, three women and two men, who were victims of priests, relatives or teachers.
The open air Mass, however, is the highlight of his six-day visit.
There are currently 24 security checkpoints in Philadelphia - police, soldiers and secret service - all trying to keep the pope safe but are they are also keeping the people away from the pope?
"It seems a little over cautious, especially giving the pope's message," visitor Charlie Affel said.
Affel had a ticket but still couldn't get in after they closed down the checkpoint.
More than a million people were predicted for the pope's Mass, the faithful hoping for a blessing.
We're learning more about the image that moved so many. Michael's father, the director of the high school band greeting the pope, just wanted his son to be in his presence.
VIDEO: Pope blesses boy in wheelchair upon arrival in Philadelphia
"Never thought this would ever, could ever happen," father Chuck Keating said.
"I was crying happy tears and I just feel so inspired," mother Kristin said.
The inspiration is continuing on Sunday, prioritizing prisoners during Pope Francis' last day in the U.S.
He arrived at the Curran-Fromhold Correctional Facility to visit with inmates and their families.
VIDEO: Pope Francis' speech to Philadelphia prisoners
After an epic celebration Saturday night, the 78-year-old pontiff is ready to do it all over again.
Mass will take place on the Benjamin Franklin Parkway at 4 p.m. ET. There will be workers transforming the stage into an outdoor cathedral, where a million people are expected to gather.
PHOTOS: Pope Francis tours Philadelphia in popemobile
LIVE UPDATES: Pope Francis in the U.S.
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