Pope Francis was greeted by the Bishop Shanahan High School marching band playing theme from "Rocky."
The marching band's pope playlist also includes Ode to Joy, Celebration, Happy and Build Me Up Buttercup.
As Pope Francis was leaving the airport, he stopped and got out of his Fiat to greet and bless a person in a wheelchair.
When the pops landed in Philadelphia, he was presented with a bouquet of Mountain Laurel, the Pennsylvania state flower.
Pope Francis has arrived at Cathedral Basilica of Saints Peter and Paul, which is considered to be Pennsylvania's largest cathedral. It was modeled after San Carlo al Corso in Rome.
Pope Francis is having lunch and spending part of the afternoon at the Saint Charles Borromeo Seminary.
The seminary has been visited Pope John Paul II and the Blessed Mother Teresa.
After serenading the pope upon his arrival, the seminarians also sang a chorus of "Happy Birthday" to Archbishop Charles Chaput.
There are 30,000 people gathered at Independence Mall to hear the pope speak, a World Meeting of Families spokesperson tells ABC News.
Pope Francis gave his speech from the same lectern used by President Lincoln to deliver the Gettysburg Address.