WASHINGTON -- Turning the page on years of war and recession, President Barack Obama summoned a divided nation Monday to act with "passion and dedication" to broaden equality and prosperity at home, nurture democracy around the world and combat global warming as he embarked on a second term before a vast and cheering crowd that spilled down the historic National Mall.

"America's possibilities are limitless, for we possess all the qualities that this world without boundaries demands," the 44th president declared in a second inaugural address that broke new ground by assigning gay rights a prominent place in the wider struggle for equality for all.

In a unity plea to politicians and the nation at large, he called for "collective action" to confront challenges and said, "Progress does not compel us to settle centuries-long debates about the role of government for all time – but it does require us to act in our time."

There were also plenty of "O-bam-a!" chants (which the president acknowledged with a smile), and, after he finished his speech, families hugged, kissed and shouted "We did it!" to no one in particular. The mood was celebratory and jovial, folks swayed along to Kelly Clarkson's performance of "My Country, 'Tis of Thee" ("That girl can sing!" one woman exclaimed to her friend), largely tuned out during Richard Blanco's Inaugural poem, and then pushed even further forward the second Beyoncé appeared onstage to sing "The Star-Spangled Banner."

While the crowd was not as large as on Inauguration Day four years ago, it was estimated at up to 1 million, it was big enough that he turned around as he was leaving the inaugural stands to savor the view one final time.