The Republican billionaire's arrival caps an extraordinary and improbable run for the White House that, once he takes the reins from President Barack Obama at noon Friday, will launch the United States into new and uncharted waters.
"The journey begins and I will be working and fighting very hard to make it a great journey for the American people," Trump, a political novice, real estate magnate and former reality television star, tweeted before leaving Trump Tower, his Manhattan home.
The 70-year-old leader-in-waiting traveled aboard an official government jet to a military base near the capital with his wife Melania.
They and several relatives headed into the city, where Trump began attending pre-inaugural festivities that have become traditions for presidents-elect.
"It is a momentous day before a historic day," said Vice President-elect Mike Pence, as Washington put its finishing touches on the downtown area where hundreds of thousands of Americans will congregate for Trump's inauguration.
After a luncheon with Republican leadership, his cabinet nominees and White House staff, Trump rode by motorcade to Arlington National Cemetery, where he and Pence laid a wreath at the Tomb of the Unknown Soldier.
He then crosses the Potomac River to speak at the Lincoln Memorial, the epicenter of Thursday's events complete with a concert and fireworks, before spending the night at Blair House, the presidential guest accommodations across the street from the White House.
"Join me at 4pm over at the Lincoln Memorial with my family!" Trump tweeted.
Trump's swearing-in on the steps of the Capitol will be carried live on screens around the globe. Rain is forecast.
Numerous dignitaries, including his unsuccessful Democratic rival for the presidency Hillary Clinton, and three former presidents will be in attendance.
Along with the crowds of Trump supporters, protesters have vowed to be out in force Friday.
Trump's working-class supporters have sent him to Washington to turn the page on the Obama era and upend the political status quo.
Trump has vowed to act, and swiftly.
He is expected to sign four or five decrees Friday, and then a raft of others beginning Monday to dismantle every policy he can without waiting for congressional approval.
Among his pledges for day one: signing orders to speed deportations of convicted criminals, begin building a wall on the US-Mexico border, and cancel billions of dollars in US funding to United Nations climate change programs.
"He is committed to not just day one, but day two, day three, of enacting an agenda of real change," incoming White House press secretary Sean Spicer told reporters.
A 'philosophical' speech
Trump's first major legislative lift will be dismantling the health care reforms known as Obamacare.
Congressional Republicans, led by House Speaker Paul Ryan, have sought for years to repeal the Affordable Care Act, and now Trump, despite potential pitfalls, is chomping at the bit.
Should Ryan pass repeal legislation, "he's actually got somebody that's going to sign it," Trump told the luncheon.
Friday will revolve around the age-old ritual of the swearing-in, when the president-elect places his left hand on a Bible, raises his right, and takes the oath of office. His inaugural address will follow.
In December, at his Mar-a-Lago estate in Florida, Trump confided that he sought inspiration from John F. Kennedy and Ronald Reagan while writing his speech.
Spicer said the words will be Trump's own, a "personal and sincere statement" that will last about 20 minutes, similar to Obama's first inaugural.
"I think it's going to be less of an agenda and more of a philosophical document, a vision of where he sees the country, the proper role of government, the role of citizens," Spicer added.
Cabinet picks complete
Obama, 55, issued a clear warning to his successor Wednesday. While he did not intend to get involved in day-to-day politics, he said he would speak out if certain red lines were crossed.
"I put in that category if I saw systematic discrimination being ratified in some fashion. I put in that category explicit or functional obstacles to people being able to vote, to exercise their franchise," he said.
The Democratic opposition is organizing. About a third of US House Democrats will boycott Friday's ceremony.
In the Senate, Democrats are obstructing the path of Trump's cabinet nominees, only a handful of whom look to be confirmed Friday. Republicans had hoped to confirm seven on that day.
Trump on Thursday named Georgia ex-governor Sonny Perdue to be agriculture secretary, a move that completes his 15 cabinet selections.
For the first time since Reagan's 1980s presidency, the cabinet will feature no Hispanics.
The new administration has asked over 50 individuals to remain in critical posts in order to "ensure the continuity of government," Spicer said, including his predecessor's special envoy to the coalition fighting the Islamic State group, Brett McGurk.
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