President-elect Joe Biden addressed the nation, just minutes after the Electoral College declared him the victor of the 2020 election and reflected on the long road it took to get to this stage.

Biden, who was awarded 306 electoral votes, commended the American public, particularly election workers and officials, for running the election during the deadliest pandemic in recent history.

"The flame of democracy was lit in this nation a long time ago, and we now know-nothing, not even a pandemic or an abuse of power can extinguish that flame," he said during the nearly 15-minute speech.

Biden noted that his Electoral College tally equaled President Donald Trump's 2016 victory.

"By his own standards, these numbers represented a clear victory then, and I respectfully suggest they do so now," he said.

Biden had harsher words for the president and some of his GOP supporters who backed his weeks of legal challenges to overturn the results of the election. He slammed the failed lawsuit issued by Texas' attorney general to invalidate votes in swing states.

"It's a position so extreme we've never seen it before, a position that refused to respect the rule of the people, refused to respect the rule of law and refused to honor our Constitution. Thankfully a unanimous Supreme Court immediately and completely rejected this effort," he said.

"The courts sent a clear signal to President Trump that they would be no part of an unprecedented assault on our democracy."

Moments after Biden secured his Electoral College victory, Trump tweeted that Attorney General Bill Barr has resigned.

"Just had a very nice meeting with Attorney General Bill Barr at the White House. Our relationship has been a very good one, he has done an outstanding job! As per letter, Bill will be leaving just before Christmas to spend the holidays with his family," Trump said in a tweet, attaching Barr's resignation letter in a thread.

The resignation comes after Trump and Barr's relationship deteriorated in the weeks following the election. Barr, earlier this month, directly undercut allegations being made by Trump and his legal team when he said the Justice Department had uncovered no evidence of widespread voter fraud that would tip the results of the presidential election.

Barr's letter praises Trump for his leadership, casts him as a victim of "partisan onslaught" and "relentless" resistance and echoes some of his most scathing criticism targeting the Russia investigation. He makes no mention of the tensions that have recently flared between the two, and even seeks to play to Trump on the way out the door, noting that their meeting was on voter fraud in the 2020 election and allegations he says are still being pursued.

Trump also announced on Twitter that Deputy Attorney General Jeff Rosen will become Acting Attorney General -- for the final five weeks of his presidency.

-ABC News' Alexander Mallin

California, a crucial vote-rich state, has officially sealed Joe Biden's victory, with the state's 55 electors delivering the president-elect the majority in the Electoral College.

By the current count, Biden now has 302 electoral votes, compared to Trump's 232.

Presiding over California's meeting as chair was Assembly Member, Shirley Weber, who announced that all 55 electors cast their votes for Biden. The room stood to clap and celebrate his victory in the state.

It's significant that it's California, Vice President-elect Kamala Harris' home state, that handed Biden his formal victory in the Electoral College -- and another blow to Trump's effort to overturn the election.

-ABC News' Kendall Karson

According to early excerpts of his speech Monday evening, Biden is expected to emphasize that the 2020 election proved that even a pandemic or "an abuse of power" can’t stop democracy from playing out.

"If anyone didn’t know it before, we know it now. What beats deep in the hearts of the American people is this: Democracy," Biden will say, according to an excerpt of his remarks. "The flame of democracy was lit in this nation a long time ago. And we now know that nothing -- not even a pandemic -- or an abuse of power -- can extinguish that flame."

Biden is expected to speak after the final state's Electoral College votes have been cast, and with his win official, will return to his call for unity and healing.

"In this battle for the soul of America, democracy prevailed. We the people voted. Faith in our institutions held. The integrity of our elections remains intact. And so, now it is time to turn the page. To unite. To heal," Biden plans to say according to a second excerpt.

The president-elect once again will pledge to be a president for all Americans and to work to address the most urgent challenges facing the country including coronavirus vaccine distribution and economic relief.

-ABC News' Molly Nagle