Barack Obama’s historic inauguration as the 44th president of the United States is underway on the steps of the US Capitol in Washington.
About one million people are watching the inauguration from the National Mall and hundreds of thousands more have packed Pennsylvania Avenue to watch the inaugural parade.
Joe Biden has been sworn in as the Vice-President of the USA, beginning a second career after 36 years in the US Senate representing the state of Delaware.
If for any reason Mr Obama is unable to continue in his job as president, Mr Biden, 66, will take the reins of the US Government.
The ceremony is taking place in a three-square-kilometre area of the capital, which has been turned into a hyper-secure zone.
More than 12,500 active troops and military reservists, thousands of metropolitan police as well as personnel from 57 departments around the nation have descended on Washington.
Earlier, Mr Obama attended a morning worship service, in honour of a tradition that began with Franklin D Roosevelt in 1933.
Then he met outgoing president George W Bush at the White House and the two went together to the US Capitol, where there were performances by Aretha Franklin, composer John Williams, and the US Navy Band and Marine Band.
After Mr Obama takes the oath of office, he will give his inauguration speech and then escort outgoing president George W Bush to a departure ceremony.
Then Mr Obama, Mr Biden and their families will attend a luncheon in the Statuary Hall of the US Capitol, along with about 200 guests, who will enjoy a menu inspired by the tastes of Mr Lincoln.
Afterwards, the 56th Inaugural Parade will travel down Pennsylvania Avenue from the Capitol to the White House.
The festivities will continue long afterwards, with the Presidential Inaugural Committee hosting 10 official inaugural balls.
The new Vice-President
Incoming Vice-President Joe Biden grew up in an Irish-Catholic family in Scranton, Pennsylvania, a former steel and mining town. He moved to Delaware at age 10 when his father relocated in search of employment.
Growing up, he was hampered by a debilitating stutter so bad he was cruelly nick-named “Dash”.
He was first elected to the US Senate at 29, in 1972, and shortly afterwards he lost his wife and baby daughter in a car crash that also left his two young sons badly injured.
Mr Biden’s down-to-earth style and appeal to traditional grassroots Democrats gave him an edge in connecting with some working-class voters who were initially wary of Mr Obama and his unusual background.
His foreign policy expertise will provide valuable help to Mr Obama in grappling with foreign policy issues such as Iraq, Afghanistan, the Gaza Strip and Iran and its nuclear ambitions.
The ABC is giving live coverage of the US Presidential inauguration on ABC Local Radio, Television and Online.