Donald John Trump was sworn in Friday as the 45th president of the US, taking office on a day that has featured smaller crowds and more subdued ceremony than previous inaugurations — but still ushers in a transformative shift in the country’s leadership.

Trump, 70, was administered the oath by Chief Justice John G. Roberts Jr. His wife Melania Trump stood at his side. The oath was given using two Bibles - one from President Lincoln’s inauguration, and another that Trump’s mother gave him in 1955, reported The Washington Post.

Earlier on Friday morning, Trump met with outgoing President Barack Obama at the White House - an Inauguration Day tradition, made more unusual this time by the two men’s history.

Trump, a real estate businessman and reality-TV star, began his rise in conservative politics by essentially calling Obama a liar and an illegitimate president: Trump insisted for years that Obama was born in Kenya.

Obama was actually born in Hawaii, as Trump conceded late in the 2016 campaign. Obama, in turn, had mocked Trump at a televised White House Correspondent’s Association dinner in 2011.

Now, they met at the White House door, one going in and one going out.

The two men and their wives took a motorcade to the US Capitol, through empty streets.

Around them, there were sporadic clashes between police and protesters around Washington. In several instances, news video showed black-clad protesters - some carrying symbols of “anarchist” groups - smashing shop windows and overturning newspaper boxes.

Earlier Friday morning, the Trumps attended a service at St. John’s Episcopal Church near the White House, continuing an Inauguration Day tradition.

One of the preachers was Robert Jeffress, a Southern Baptist minister who is pastor of a Dallas megachurch, and who has made inflammatory condemnations of both Mormonism and Islam in the past.

Jeffress, who grew close to Trump during the 2016 presidential campaign, said on Twitter that his sermon would be entitled, “When God Chooses a Leader.” Trump left the service about 9:30 a.m. He mouthed “Thank you” to supporters as he climbed into an SUV.

Before Trump and Vice President Mike Pence took their respective oaths, Senator Roy Blunt (R-Mo.) – who oversaw inauguration preparations on Capitol Hill – offered a brief speech praising the American tradition of peaceful transfer of power.

“Commonplace and miraculous,” Blunt called it, recalling the early, key transitions between early American presidents of different parties. That made inauguration ceremonies, Blunt said, “not a celebration of victory, [but] a celebration of democracy.”

President Trump will later attend a luncheon at the Capitol, and his inaugural parade down Pennsylvania Avenue will begin about 3 p.m. That parade is supposed to last about 90 minutes — which would make it one of the shortest inaugural parades in recent history.

Signs of the transfer of power were evident throughout the morning.

Before 9:30 a.m., TV footage showed Obama leaving the Oval Office for the last time, before he and the first lady held a pre-inauguration tea with the Trumps.

Obama smiled as he walked down an exterior hallway, in view of cameras. “Any last words for the American people?” a member of the press called out. “Thank you,” Obama said.

Soon after, the Trumps arrived at the White House, greeting the Obamas and presenting them with a gift — a box wrapped in the distinctive light blue of high-end jeweler Tiffany & Co. The Obamas seemed briefly perplexed about what to do with it, with the president looking in vain for someone to hold the box while the new first couple and the old took a photo together.

Since Trump’s election, both men have tried to mend their relations, including with a high-profile meeting days after Trump’s stunning election.

On the White House steps, the bitter history between Trump and Obama went unmentioned. Obama asked Trump, “How was church?” and they turned to go inside.

Trump’s swearing-in will give Republicans control of both the White House and Congress for the first time since 2006.

The new president has promised to undo some of the most significant pieces of Obama’s legacy - including his signature health-care law. But Trump also enters office with a significant amount of uncertainty, since he has repeatedly contradicted other Republicans - and himself - on major questions about how immigration, taxes, health care and other issues will be handled in the new administration.

Exhorting thousands of supporters at the conclusion of an evening concert that was punctuated by a glimmering fireworks display, Trump vowed, “We’re going to work together, and we are going to make America great again - and, I’ll add, greater than ever before.”

Trump and his extended family on Thursday signaled a new era in the country’s governance as they stepped off a military plane at Joint Base Andrews.

They headed directly to his Pennsylvania Avenue property, the Trump International Hotel, where the president-elect irreverently toasted his Cabinet nominees.

“We have by far the highest IQ of any Cabinet ever assembled,” Trump said in a characteristically grandiose - and unprovable - declaration before several hundred supporters, lawmakers and allies at an official luncheon. He scanned the room for familiar faces and riffed on each individually, as if he were delivering a toast.

Trump narrated his journey and the day’s festivities on Twitter. “On my way!” Trump tweeted as he headed in the afternoon to Arlington National Cemetery, where he and Vice President-elect Mike Pence laid a wreath at the Tomb of the Unknowns. They both stood in silence with their hands over their hearts as a bugler played taps.

Earlier that day, as Trump put the finishing touches on the inaugural address he will deliver from the steps of the Capitol after taking the oath of office at noon Friday, Pence and their incoming administration were preparing to assume control of the federal government.

Addressing reporters Thursday from the transition team’s Washington headquarters, Pence said, “It is a momentous day before a historic day.”

He noted that all 21 Cabinet nominations have been made and that 536 “beachhead” officials are ready to report for duty at federal departments and agencies.

“Our job is to be ready on Day One,” Pence said. “The American people can be confident that we will be.  It’s going to be a very humbling and moving day for the president-elect his family and for mine. But let me tell you, we are all ready to go to work,'” he stated.

Trump and his team on Thursday sent signals suggesting an attempt to begin repairing relations with groups he demonized throughout his transition, including the intelligence community and the media.

Sean Spicer, the incoming White House press secretary, calmly answered questions for an hour in his first formal briefing with journalists and confirmed that Trump would soon visit the CIA’s headquarters in Langley, Va., to express his gratitude to career intelligence officers.

While the bureaucrats-to-be were working, Trump supporters from throughout the country who had descended on Washington were partying at the concert at the Lincoln Memorial, which was bathed in patriotic lighting.

Throngs of people extended toward the Washington Monument as an assortment of military bands and recording artists performed.

As Trump and his wife, Melania, descended the monument’s steps at sunset, the president-elect saluted the marble statue of President Abraham Lincoln, flashed a tight smile and pumped his fist in the air to the roar of the crowd and the Rolling Stones’ “Heart of Stone” playing from the speakers.