PHILADELPHIA (AP) - (AP) -- He spoke at Independence Hall, where the Declaration of Independence and the Constitution were signed. He stood at the very lectern Abraham Lincoln used to deliver the Gettysburg Address. And he stepped forward to the stirring strains of "Fanfare for the Common Man."

In a scene rich with historical symbolism, Pope Francis arrived in the City of Brotherly Love on Saturday, offering warm and affectionate words of welcome to immigrants and extolling America's founding ideals of liberty and equality.

"Those ringing words continue to inspire us today," the pope said of the Declaration of Independence, "even as they have inspired peoples throughout the world to fight for the freedom to live in accordance with their dignity."

He cited the abolition of slavery, the growth of the labor movement and the fight for racial equality as proof that "when a country is determined to remain true to its founding principles, based on respect for human dignity, it is strengthened and renewed."

At the same time, Francis warned that religious freedom is under threat. But it was not the hard-hitting discussion some conservative American bishops may have wanted to hear.

Loath to get dragged into domestic culture wars, the pope did not mention gay marriage, abortion or government-mandated birth control coverage by name, speaking of threats to religious liberty in broader, more global terms.

He decried "a world where various forms of modern tyranny seek to suppress religious freedom, or try to reduce it to a subculture without right to a voice in the public square, or to use religion as a pretext for hatred and brutality."

Using the occasion instead to embrace other causes close to his heart, Francis encouraged immigrants in the crowd of 40,000 to celebrate their heritage and traditions, and he assured them they are of value to America.

"By contributing your gifts, you will not only find your place here, you will help to renew society from within," the first pope from Latin America said in his native Spanish.

On Saturday night, tens of thousands gathered on the wide Benjamin Franklin Parkway for a music-and-prayer festival featuring Aretha Franklin, Italian tenor Andrea Bocelli and actor Mark Wahlberg.

Sitting on a huge throne, Francis listened to the entertainment and to several families tell their stories of joys and troubles.

But in an indication that Francis was lagging from the exhaustion of a weeklong trip to Cuba and the U.S., the program was trimmed after it ran more than an hour late and Francis ditched his prepared remarks to instead deliver an off-the-cuff monologue on families and God's love.

He called families a "factory of hope," even with their imperfections.

"Defend the family, because that's where our future will play out," he said.

After he finished, a chant erupted from Logan Square: "¬°Viva El Papa, Viva La Familia!"

Francis came to Philadelphia to close out the World Meeting of Families, a Vatican-sponsored conference of more than 18,000 people from around the world. He found a city practically under lockdown, with blocked-off streets and checkpoints manned by police, National Guardsmen and border agents.

There had been fears that visitors might be scared away by the security, and, in fact, train ridership was lower than expected, some streets were eerily quiet and a vendor of pope sunglasses cut his price from $15 to $10 for lack of business.

It remains to be seen if the expected 1 million people turn out for Francis' final Mass in the U.S., on the Parkway on Sunday.

Earlier in the day Saturday, the pontiff arrived from New York at the Philadelphia airport, where a Catholic high school band launched into the theme song from the Philadelphia-set movie "Rocky." Among those greeting him was Richard Bowes, a former Philadelphia police officer wounded in the line of duty. Francis also kissed the forehead of a 10-year-old boy severely disabled with cerebral palsy.

Then he celebrated a Mass for about 1,600 people at the Cathedral Basilica of Sts. Peter and Paul, saying in his homily that the future of the Catholic Church in the U.S. requires a much more active role for lay Catholics, especially women.

"It means valuing the immense contribution which women, lay and religious, have made and continue to make to the life of our communities," he said.

Francis has repeatedly said women should have a greater role in church leadership, though he has rejected the idea of ordaining women. By calling for more involvement of women and the laity, he seemed intent on healing one of the major rifts in American Catholicism that have alienated many from the church.

Later in the day, he traveled to red-brick Independence Hall in his open-sided Jeep, rolling slowly past adoring crowds and kissing babies handed to him by members of his security detail.

During the first two legs of his U.S. visit, in Washington and New York, he addressed Congress and the United Nations, urging action on such global issues as climate change and economic inequality. The Philadelphia visit is expected to be more personal, more focused on ordinary Catholics and their families.

"He has a magnetic personality that not only appeals to Catholics, but to the universal masses. He's not scripted. He's relatable," said Filipina Opena, 46, a Catholic from LaMirada, California.

Tony Coletta, a 62-year-old Philadelphia-area surgeon and health care company CEO who helped raise money for the papal visit, said: "I believe that he's going to bring the Catholic Church back in America in a way that nobody's ever seen before. His message resonates. It's much more of an all-encompassing one. And the small things that he does, spending time with the poor, it's more than just symbolic."

The Archdiocese of Philadelphia organized the conference, hoping for a badly needed infusion of enthusiasm amid shrinking membership, financial troubles and one of the worst clergy sex-abuse scandals to hit a U.S. diocese.

The archdiocese has been the target of repeated investigations. In 2011, before Archbishop Charles Chaput came to Philadelphia, a grand jury accused the diocese of keeping on assignment more than three dozen priests facing serious abuse accusations.

A monsignor who oversaw priest assignments was found guilty of child endangerment, becoming the first American church official convicted of a crime for failing to stop abusers.

The pope is widely expected to talk privately with abuse victims this weekend.

The visit is also shaping up as one of the most interesting ecclesial pairings of the pope's trip. His host is Chaput, an outspoken opponent of abortion and gay marriage who takes an especially hard line.

Francis has strongly upheld church teaching on such issues but has struck a more compassionate note, saying, "Who am I to judge?" when asked about a supposedly gay priest.

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Contributing to this report were Associated Press writers Rachel Zoll in New York and Kathy Matheson and Maryclaire Dale in Philadelphia.