Bringing a message that America's power and wealth should be used to serve humanity, the 78-year-old pontiff said the United States must not turn its back on "the stranger in our midst."
"Building a nation calls us to recognize that we must constantly relate to others, rejecting a mindset of hostility," Francis told the Republican-led Congress in Washington a day after he met with Democratic President Barack Obama.
Francis, born in Argentina to an Italian immigrant family, delivered a wide-ranging speech that addressed issues dear to liberals in the United States but also emphasized conservative values and Catholic teachings on the family.
The leader of the world's 1.2 billion Roman Catholics called for a worldwide end to the death penalty, which is still used in 31 of the 50 US states, while advocating a more equitable economy to help people "trapped in a cycle of poverty" and a greater effort against climate change driven by human activities.
The pope later flew to New York, where he was cheered by throngs lining Fifth Avenue as he headed in his "popemobile" to St. Patrick's Cathedral to the sound of the cathedral bells pealing. With organ music playing and a chorus singing, the pope was welcomed by a crowd of 3,000 inside the cathedral for an evening prayer service.
Francis on September 25 is due to address the United Nations General Assembly in New York and to celebrate an open-air Mass in Philadelphia on September 27.