Biden, for the first time as the 46th president of the United States, has arrived at the White House, his expected home for the next four years. He held hands with the first family, all donning masks, as they walked the final blocks.

As they walked through the northwest gate, a reporter asked what his message was to the world, and Biden replied, "Unity."

A U.S. Army band played "Hail to the Chief" as Biden and Jill Biden stood in front of the North Portico doors. The couple embraced before the rest of the first family joined them, and together, they walked inside the White House.

The day's inaugural ceremonies are set to continue into the night.

Biden is slated to sign executive orders in the Oval Office Wednesday evening and swear-in Day One appointees in a virtual ceremony. Biden and Harris are then scheduled to deliver remarks before 9 p.m. during the "Celebrating America" inaugural program and close the night out with a wave to the nation from the Blue Room Balcony.

Unlike previous administrations, Biden comes into office without any of his Cabinet nominees confirmed. As he enters the White House, his nominees enter Day One performing in an acting capacity.

As Biden and Harris receive their first presidential escort to the White House, they're surrounded by a fortified Washington, D.C.

At least 25,000 National Guard members are in the District to safeguard the inaugural ceremonies after a seige on the U.S. Capitol two weeks ago heightened security concerns.

And at least a dozen Army National Guard members were removed from the inauguration security mission this week, including two members who were sent home after vetting uncovered extremist links, a Pentagon official said Tuesday.

-ABC News' Luis Martinez

The newly-anointed first and second families are at Arlington National Cemetery for a wreath-laying ceremony at the Tomb of the Unknown Soldier.

Biden and Harris are accompanied by all living former presidents -- other than now former President Donald Trump, who landed in his Florida Resort earlier in the day without greeting Biden, and former President Jimmy Carter, who spoke with Biden and sent his well wishes but was unable to travel due to coronavirus concerns.

Former President Barack Obama and Michelle Obama, former President George W. Bush and Laura Bush, and former President Bill Clinton and former Secretary of State Hillary Clinton joined now President Biden and Vice President Kamala Harris in a historic moment at the solemn site. At the start of the ceremony, a military band played the "National Anthem" and "Taps."

When Biden's motorcade arrived, now with a "46" on the limo's license plate, smoke from the traditional 21-gun salute drifted through the air.

In another customary event, Biden -- the nation's new commander in chief -- reviewed the readiness of troops from the steps of the Capitol's East Front.

Pass in Review is a military tradition in which the incoming president reviews the readiness of military troops with every branch of the military represented in the demonstration.

At the conclusion of the inauguration ceremonies on Capitol Hill, troops in Revolutionary War-era uniforms, some with instruments -- and all in masks -- marched before the first and second families to the tune of "Yankee Doodle Dandy."

Following the pass, Biden, Harris and their families headed to Arlington National Cemetery to lay a wreath at the Tomb of the Unknown Soldier. In a show of unity, former President Barack Obama and Michelle Obama, former President George W. Bush and Laura Bush, and former President Bill Clinton and former Secretary of State Hillary Clinton joined them.

The president and first lady emerged from the White House shortly before 10 p.m. to watch a fireworks display that ended the inaugural festivities on Wednesday night.

While the Bidens were on the Blue Room Balcony, the vice president and second gentleman watched from the steps of the Lincoln Memorial, where Harris had spoken to the public a few minutes earlier and where Katy Perry was performing her song, "Firework."