President Barack Obama ushered in a new era for the United States, becoming the first black leader of the country founded by slave-owners, and telling the world America is "ready to lead once more" after eight divisive years under George W. Bush.

Taking the helm of a nation beset by economic troubles and two wars, Obama told Americans on Tuesday that "starting today, we must pick ourselves up, dust ourselves off and begin the work of remaking America."

Before a crowd that swelled to more than 1 million on the National Mall, Obama assumed power over a nation longing for change after an era that that witnessed the September 11, 2001 terror attacks, the beginning of wars in Afghanistan and Iraq and an economic collapse not seen since the 1930s Great Depression.

From Kenya and Indonesia, where Obama has family ties, to Asia, Europe, Africa and Latin America, his inauguration sparked a volcanic explosion of hope for better days ahead. People around the world gathered in front of their television sets to witness the moment in history, and Obama addressed them directly.

His speech took note of his historic place as the first black president in understated but deliberate language, and he spoke of himself as "a man whose father less than 60 years ago might not have been served at a local restaurant" yet one who now could take its most sacred oath.

Immediately after the inauguration ceremony, Bush and his wife, Laura, boarded a helicopter alongside the US Capitol, as they began their journey home to Texas. The new president and his wife walked them to the chopper?- keeping with tradition?- to see them off.