The archbishop of Denver since 1997, Chaput succeeds Cardinal Justin Rigali, whom he praised as "one of the great churchmen of my lifetime."
He will be installed Sept. 8 as head of the 1.5 million-member archdiocese in Philadelphia, Bucks, Montgomery, Delaware, and Chester Counties.
His voice choking briefly, Chaput said that "leaving a place is easy," but that "leaving people [in Denver] who have shaped me with their friendship . . . that's very, very hard."
Rigali, 76, who introduced Chaput at the news conference, appeared tired and drawn despite his broad smiles. The grand jury sharply criticized him in February, saying he had failed to adequately investigate allegations against dozens of priests accused of sex abuse and other misconduct with children.
"I apologize for any weaknesses on my part," he said, adding that it is "a formidable task to be a bishop. You ought to try it."
In March, Rigali suspended more than two dozen priests pending an archdiocesan investigation. Gina Maisto Smith, the former Philadelphia prosecutor who is leading that investigation, said after the news conference that her team expected to continue its work despite the change of archbishops.
With her findings still months away, she said, it appears that it will fall to Chaput to decide whom among his priests to dismiss and whom to restore to ministry.
Archbishop here since 2003, Rigali will lead the archdiocese as apostolic administrator until Chaput's installation, then retire to the Diocese of Knoxville, Tenn., at the invitation of Bishop Richard Stika, a friend. He will remain a cardinal for life, and may continue to serve on Vatican congregations and as a papal elector until he turns 80.
In response to questions from reporters, Chaput said he had not read the devastating 2011 or 2005 Philadelphia grand jury reports on clergy sex abuse and its cover-up, but would do so soon. He said he would meet with victims of abuse and their families.
He also said he looked forward to getting to know his priests and "the issues" of the archdiocese. As in many other dioceses in the Northeast, Philadelphia's Catholic population has been static for many years, and many parishes and schools have been closed because of declining enrollment.
Chaput said it was too soon to describe his designs for his new archdiocese. Citing a jest by a famous physicist, he observed that "prediction is difficult - especially about the future."
But later he remarked that his two American Indian names - he is a member of the Potawatomi tribe on his mother's side - mean Good Eagle and Wind That Rustles.
"That's who I am," he joked. "A good eagle who rustles the leaves."
At the news conference, a group of high school and college students presented him with the Philadelphia sports team hats, and chided him for his known allegiance to the Pittsburgh Steelers and Denver Broncos football teams.
Afterward, he mingled with the audience. "Do you all work for me?" he asked a group of archdiocesan employees, who laughed and nodded and pumped his hand.
Later he joined in saying Mass at the Cathedral Basilica of SS. Peter and Paul. Although Chaput is now archbishop of Philadelphia, by custom Rigali served as principal celebrant and sat in the bishop's seat.
"You welcome him just as you welcomed me eight years ago," he said in his brief homily, and asked the members of the archdiocese to pray for their new archbishop.
At the start of the Mass, security guards removed a barefoot woman who moments earlier had placed a red rose on the altar and then approached Rigali and Chaput as they proceeded through the Communion rail.
Chaput, who sat alone at a side chair, did not address the crowd of about 450, but helped to dispense Communion.
"I'm sure he'll do wonderful work with the backing of all of us," Antonia Pugliese, 67, a member of the cathedral parish, said after the Mass. "But he'll have his work cut out for him."
See a video about Philadelphia's new archbishop at www.philly.com/chaput
Contact staff writer David O'Reilly at 215-854-5723 or firstname.lastname@example.org.