Now the hard work begins. It might have sounded like Donald Trump's aides were joking when they said he would only attend three balls today because he was busy, but he really does have a lot to do.
Here are some of Trump's promises:
Build the wall
Trump said: 'We will bring back our borders.' But his campaign pledge to build 'an impenetrable, physical, tall, powerful, beautiful, southern border wall' between the US and Mexico was not mentioned.
Keen to placate gun rights supporters, Trump has promised to abolish gun-free zones around schools and on military bases. 'My first day, it gets signed - no more gun-free zones,' he has said. He says gun-free zones are a magnet for mentally-ill gunmen.
Bring back jobs
Trump pledged yesterday to rebuild America 'with American hands' and 'follow two simple rules - buy American and hire American'. His promise to help jobless American workers in the country's depressed heartland was, for many voters, his most important pledge. Critics say it will also be the trickiest as many of those manufacturing jobs appear to have moved to lower-wage countries for good. The President has vowed personally to call the bosses of major US firms who plan to move jobs overseas and warn them they face a 35 per cent tariff if they go ahead.
Drain the swamp
His 100-day action plan included six measures to tackle what he sees sleaze and corruption. They include a constitutional amendment to impose terms limits on all Congress members, a hiring freeze on all federal government employees, restrictions on the creation of new regulations and a limit on the lobbying activities of White House and congressional officials after they leave office.
Protect US trade
He has promised to immediately renegotiate or withdraw from the North America Free Trade Agreement, the deal that governs commerce with, among others, Mexico. He has also vowed to dash plans to take the US into the Trans-Pacific Partnership.
The special relationship
Trump pledged to 'reinforce old alliances'. He did not mention Britain by name but has previously said he will make an agreement with the UK a priority. Yesterday, however, he did not endorse Foreign Secretary Boris Johnson's recent boast to have secured a pledge that the UK would be at the 'front of the line' for a trade deal.
Decisions on immigration 'will be made to benefit American workers and American families', Trump said, although he added: 'When you open your heart to patriotism, there is no room for prejudice.' In recent weeks, he has backed away from his call for a temporary ban on Muslim visitors entering the country. Instead, he has said he plans from his first day in office to suspend immigration from 'terror prone' countries and impose 'extreme vetting' on others.
Barack Obama's Affordable Care Act, reforming America's famously complicated and expensive health insurance system, was his administration's most radical achievement. It guarantees health coverage for all Americans but has landed many people with higher bills. Trump intends to scrap it.
One of the few areas where Trump is likely to get Democrat support is his pledge to spend $1trillion over the next decade on investing in America's crumbling infrastructure. In his speech, he pledged to 'build new roads, highways, bridges, airports, tunnels and railways'. Such huge spending will surely complicate his plans to slash taxes, especially for business, without plunging the US further into the red.
Trump has previously questioned the existence of global warming, describing it as a hoax dreamt up by China. Last night, confirming the fears of many environmentalists, the White House website had already signalled President Trump's intentions on climate change, saying he is 'committed to eliminating harmful and unnecessary policies such as the Climate Action Plan and the Waters of the US rule'. Mr Trump has promised to tell the United Nations that the US will no longer be contributing money towards its climate change programmes.
A new missile defence system
One of Trump's first moves was to announce plans for a missile defence system to protect the US against attacks from Iran and North Korea. The announcement on the White House website contained no further detail about the measures being planned. It remains unclear whether it could be a ground- or air-based system - or, more controversially, satellite-based like Ronald Reagan's Strategic Defence Initiative, better known as 'Star Wars'. First announced in 1983, Star Wars was intended to protect the US against Soviet aggression during the Cold War.