From the BBC vaults: four inaugural moments
The BBC has reported from multiple inaugurations of US presidents. A look at our coverage at the edges of these historic occasions.
Thomas Jefferson was the first president to be inaugurated in Washington DC, but even before that the presidential swearing in was an important public ceremony.
The ability to change leadership every four to eight years without conflict or protest is one of the crowning achievements of American democracy.
For decades, the BBC has reported from Washington as the next President of the United States is sworn into office. This year, we've combed our archives to bring you four snapshots of the American transition of power, from the second swearing in of Richard Nixon to the hope and change of Barack Obama.
1973: Richard Nixon
Money has always been an important part of American politics - and not just in terms of the campaign for votes at election time.
The inauguration of the new president also costs money. Back in 1973, the festivities for the second swearing-in of President Nixon amounted to an estimated $2.4m (£1.5m).
The BBC's John Humphrys previewed the event, noting how it would cost £20 for a seat near the speech and £200 for a box at the presidential ball.
1981: Ronald Reagan
For 444 days, fifty Americans had been held hostage in Iran. The kidnapping and subsequent failed rescue attempt was seen by many as a pivotal reason for Jimmy Carter's failed re-election bid against challenger Ronald Reagan.
Then, minutes after Reagan was sworn in as president, he was informed that the American hostages had been freed.
He made the announcement during the inaugural luncheon, saying "Some 30 minutes ago, the planes bearing our prisoners left Iranian air space, and they're now free of Iran."
In this extract of a report by the BBC's Martin Bell we see how the inauguration turned into a double celebration - as well as some state-of-the-art television tricks from 1981.
1993: Bill Clinton
After the successful conclusion of the first Iraq War, the re-election of George HW Bush seemed a foregone conclusion. But two short years later, it was William Jefferson Clinton who was inaugurated on January 20, 1993. It would be the beginning of a rejuvenation of the Democratic party spearheaded by the Clinton family.
It would also, some analysts say, kick off long-lasting partisan battles.
Jeremy Paxman presented BBC Newsnight on the night of Clinton's first inauguration, describing the festivities as "schmaltzy, naive, yet exhilarating" and the president's speech as one that "read better than it sounded".
2009: Barack Obama
Barack Obama won the highest percentage of the popular vote since George HW Bush in 1988. A small percentage of those supporters came out to celebrate on his inauguration day, but it was still enough to set a record for the most people on the mall.
The turnout might have been even greater if the thermometer ever inched above freezing. But despite the bitter cold, the Obama family walked the parade route to throngs of cheering fans. And Gavin Hewitt found supporters, wrapped in hats, gloves and blankets, willing to line up before sunrise to get a good look at the new president.
This year, the temperature will be warmer, but the political climate in Washington is exceptionally chilly.
The crowds are smaller, but the expectations on the president are just as large.