WATCH: 'Field of Flags' lighting ceremony honors U.S. states and territories ahead of Biden's inauguration

The completed "Field of Flags" display on the National Mall in Washington DC was lit up by powerful beacons on Monday.

Watch the lighting ceremony in the player above.

The display was organised by the Presidential Inaugural Committee to mark the upcoming swearing-in of President-elect Joe Biden.

Echoing the "America United" theme of inauguration week, the display features 191,500 US flags and 56 pillars of light.

The pillars symbolise every U.S. state and territory, according to the Committee.

It added the display represented all Americans unable to travel to Washington DC to attend the inauguration due to the coronavirus pandemic.

The theme for the inauguration will be "America United," an issue that's long been a central focus for Biden but one that's taken on added weight in the wake of the violence at the U.S. Capitol last week.

In an announcement shared first with The Associated Press, the Presidential Inaugural Committee said that the theme reflects the beginning of a new national journey that restores the soul of America, brings the country together, and creates a path to a brighter future.

Alexandra Jaffe, a national political reporter for the Associated Press, said the artwork will be overcast by fences and armed guards protecting the area for the event.

"It's a pretty striking juxtaposition of what I think Biden would describe as the hope of America and what America really has been for the past couple of weeks," Jaffe said.

In keeping with the theme of unity, the committee also announced that after he is officially inaugurated, Biden, Vice President-elect Harris, and their spouses will lay a wreath at the Tomb of the Unknown Soldier in Arlington National Cemetery, and will be joined there by former Presidents Barack Obama, George W. Bush, Bill Clinton, and their wives.

It will be one of Biden's first acts as president, and a show of bipartisanship at a time when the national divide is on stark display.

The focus on unity has characterized Biden's presidential run from the start, and he's said repeatedly since winning the White House he sees unifying the country as one of his top priorities as president.

But the scope — and urgency — of the challenge Biden faces became even clearer this week after President Donald Trump sparked an armed insurrection at the Capitol, spurred by his repeated attempts to delegitimize Biden's win.

Matthew Costello, a lead historian with the White House Historical Association, said the closest comparison to the riot would be both of Abraham Lincoln's inaugural addresses which happened before and during the Civil War.

"If ever there was an opportunity for a president to renounce and denounce the Confederacy, to denounce insurrection, to denounce people who decided to raise arms against the United States government, he doesn't do it," Costello said.

"Lincoln calls for reconciliation, he alludes to this idea that all Americans are responsible for the Civil War, not just the South."

Security at Biden's Inauguration will be tight. The National Park Service announced Monday it would shut down public access to the Washington monument until Jan. 24, citing threats surrounding the inauguration.

"Biden has expressly asked Americans to stay home because of the coronavirus pandemic. So you weren't going to see the crowds, you weren't going to see the parade," said Jaffe.

Trump himself is skipping Biden's inaugural, a decision Biden said was a "good thing," though Vice President Mike Pence and his wife plan to attend.

"(Pence) and his wife will be attending the inauguration again in a show of bipartisan support for Joe Biden's legitimacy and in keeping with a peaceful transition of power that I think all Americans expect and that we want to see on Inauguration Day," Jaffe said.

It's not the only COVID-era change to the festivities. In keeping with crowd-size restrictions to slow the spread of the virus, Biden will have a significantly pared-down inauguration, with traditional activities like the parade and the inaugural balls moving to a virtual format.

But even as the celebration itself will be smaller, inauguration officials are preparing a significant security presence in preparation for what may be more pro-Trump demonstrations across Washington.