Pope Francis focused his first public remarks in the United States on the urgent need to counter climate change, largely steering clear of some of the more contentious political issues gripping the country.
Speaking at the White House just before a private meeting with President Barack Obama on Wednesday (Sept 23), he stressed that climate change is a problem that can no longer be left to future generations.
"When it comes to decay of our common home, we are living at a critical moment of history," he said in a rare speech in English.
"We still have time to make the change needed to bring about a sustainable and integral development, for we know things can change. Such change demands on our part a serious and responsible recognition, not only of the kind of world we may be leaving to our children, but also to the millions of people living under our system which has overlooked them."
He touched briefly on the importance of the family institution and described the US as a country of immigrants, but otherwise left issues like gay marriage and immigration alone.
Mr Obama, who spoke before the Pope, paid tribute to the "profound moral example" he has set.
"All of us may, at times, experience discomfort when we contemplate the distance between how we lead our daily lives and what we know to be true and right. But I believe such discomfort is a blessing, for it points to something better. You shake our conscience from slumber," he said in front of some 15,000 invited guests at the White House south lawn.
Tens of thousands had gathered at the National Mall as early as 4am, some five hours before a short papal parade was set to take place.
Ms Catherine Everitt, 32, who works at a non-profit organisation, turned up at 3.30am with a religious scroll she hoped the Pope would bless as he passed.
"How often do you get a Pope coming to your city? There is no way I was going to miss this."
The pomp of the Pope's White House visit was in stark contrast to his unassuming arrival at Joint Base Andrews outside Washington a day earlier. Though the President, who usually waits at the White House, Vice-President Joe Biden and their families turned out to greet the Pope as he stepped off the plane from Cuba, it was a relatively low-key ceremony. Just a few hundred invited guests and students from local Catholic schools were allowed into the base, with only four children picked to meet the Pope up close.
What was perhaps most eye-catching for an American audience used to dignitaries in large luxury limos was the Pope's choice of vehicle - a Fiat 500L compact car.
The most anticipated part of Pope Francis' first visit to the US will come when he addresses a joint session of Congress later today.
After Washington, he heads to Philadelphia before wrapping up his visit with remarks at the United Nations meeting in New York.