Donald Trump was sworn in as the 45th president of the United States on Friday, succeeding Barack Obama and taking control of a divided country in a transition of power that he has declared will lead to "America First" policies at home and abroad.
As scattered protests erupted elsewhere in Washington, Trump raised his right hand and put his left on a Bible used by Abraham Lincoln and repeated a 35-word oath of office from the U.S. Constitution, with U.S. Chief Justice John Roberts presiding.
At Trump's side was his wife, Melania Trump.
The transition from a Democratic president to a Republican took place on the West Front of the domed U.S. Capitol before a crowd of former presidents, dignitaries and hundreds of thousands of people on the grounds of the National Mall. The crowd stretched westward on a cool day of occasional light rain.
Clinton attended the ceremony with her husband, former President Bill Clinton.
Trump, 70, takes over a country divided after a bitter election campaign. A wealthy New York businessman and former reality TV star, he will set the country on a new, uncertain path at home and abroad.
"It all begins today!" he wrote in a note on Twitter at about 7:30 a.m. on Friday "I will see you at 11:00 A.M. for the swearing-in. THE MOVEMENT CONTINUES - THE WORK BEGINS!"
Away from the Capitol, masked activists ran through the streets smashing windows with hammers at a McDonald's restaurant, a Starbucks coffee shop and Bobby Van's Grill steakhouse several blocks from the White House.
They carried black anarchist flags and signs that said, "Join the resistance, fight back now." Police used pepper spray and chased them down a major avenue, a Reuters eyewitness reported.
In another location not far from the White House, protesters also scuffled with police, at one point throwing aluminum chairs at them at an outdoor café.
At the inaugural ceremony, former presidents George W. Bush and Jimmy Carter were also present with their wives. Bush's father, former President George H.W. Bush, 92, was in Houston recovering from pneumonia.
Trump and his vice president, Mike Pence, began the day attending a prayer service at St. John's Episcopal Church near the White House.
Trump, wearing a dark suit and red tie, and Melania Trump, clad in a classic-styled, powder blue ensemble, then headed into the White House for a meeting with Obama and his wife, Michelle.
Trump takes office with work to do to bolster his image.
During a testy transition period since his stunning election win on Nov. 8, Trump has repeatedly engaged in Twitter attacks against his critics, so much so that one fellow Republican, Senator John McCain, told CNN that Trump seemed to want to "engage with every windmill that he can find."
An ABC News/Washington Post poll this week found only 40 percent of Americans viewed Trump favorably, the lowest rating for an incoming president since Democrat Carter in 1977, and the same percentage approved of how he has handled the transition.