At 2020’s dawn, the United States was in the middle of impeachment proceedings against President Donald Trump. Impeachments are historic, but 2020 made this one seem more like a historical footnote. After competing wings wrestled for control of the Democratic Party, former Vice President Joe Biden gained its nomination for president. Meanwhile the country faced the death of a Supreme Court justice, the confirmation of her replacement, the coronavirus’s effect on a wild campaign, and an election the Trump campaign has since characterized as “rigged” for Biden, despite failing to offer substantive proof. With Senate control still undetermined, 2020 closes with ­Americans even more divided than when the year began.

Nick Wagner/Austin American-Statesman via AP

Campaign trail

Lily Barbour, 5, holds a campaign sign for Democratic presidential candidate Sen. Bernie Sanders, I-Vt., during a campaign event on Feb. 23 in Austin, Texas. Sanders, having just won the Nevada Democratic caucuses and the New Hampshire Democratic primary, was the front-runner for the Democratic presidential nomination.

Evan Vucci/AP

Acquitted

At the National Prayer Breakfast on Feb. 6, President Donald Trump holds a newspaper showing the U.S. Senate acquitted him of two articles of impeachment the day before. Both the House’s vote to impeach Trump in December 2019 and the Senate’s vote to acquit went mostly along party lines.

Patrick Semansky/AP

Heated debates

Democratic presidential ­candidates Pete Buttigieg, Sen. Elizabeth Warren, D-Mass., and Sen. Bernie Sanders, I-Vt., spar at a debate in Charleston, S.C., on Feb. 25. Four days later, ­former Vice President Joe Biden won the state’s primary, propelling him to front-runner status.

Andrew Harrer/Bloomberg via Getty Images

Virtual lead

Joe Biden speaks during a ­virtual campaign event on April 13 during which Bernie Sanders endorsed him, making Biden the presumptive Democratic nominee for ­president. By the spring, the Biden presidential campaign stopped in-person events and shifted online because of the escalating coronavirus pandemic.

Amr Alfiky/The New York Times via AP

Masked civility

Former Vice President Joe Biden and current Vice President Mike Pence greet each other in masks and with an elbow bump at a ceremony in New York to observe the 19th anniversary of the Sept. 11 attacks. The coronavirus limited how the Biden and Trump campaigns operated and altered protocols for presidential and vice presidential debates.

Jose Luis Magana/AP

Supreme Court struggle

Demonstrators for and against the confirmation of Amy Coney Barrett to the United States Supreme Court rally on Capitol Hill on Oct. 14. President Donald Trump ­nominated Barrett after the death of Justice Ruth Bader Ginsburg on Sept. 18.

Tom Williams/AP

Note-free

Amy Coney Barrett shows her blank notepad as she speaks during her confirmation hearing before the Senate Judiciary Committee on Oct. 13. When Sen. John Cornyn, R-Texas, asked Barrett what reference material she was using to answer the committee’s questions, she revealed the blank notepad, confirming she was answering from her own knowledge. The full Senate confirmed Barrett to the Supreme Court on Oct. 26 in a 52-48 vote.

Evan Vucci/AP

Campaigns continue

President Donald Trump ­gestures before speaking at a campaign rally in Winston-Salem, N.C., on Sept 8. He and Joe Biden battled for the Tar Heel State, which Trump won on Election Day by less than 2 percent of the vote.

Jason Connolly/AFP via Getty Images

Election Day

Steph Smith drops off her ballot for president at a special ballot box in Rollinsville, Colo., on Nov. 3. The coronavirus pandemic prompted more remote and mail-in voting, which became the center of election controversy.

Paula Bronstein/AP

Vote tallies

Election worker Kristen Mun empties ballots from a bin in Portland, Ore., on Election Day. U.S. voters cast a record 65 million mail-in votes due to the coronavirus pandemic.

Adriana Zehbrauskas/The New York Times/Redux

Vote challenges

Supporters of President Donald Trump rally at City Hall in Phoenix on Nov. 5. Trump and his allies filed dozens of legal challenges to vote counts in several states in the weeks after the election. Despite claims of widespread voter fraud, courts overwhelmingly rejected the Trump campaign’s legal arguments.

Jacquelyn Martin/AP

Biden’s win

People launch fireworks in Washington, D.C.’s Black Lives Matter Plaza on Nov. 7, celebrating President-elect Joe Biden’s win. The Associated Press and other news outlets projected that day that Biden had won Pennsylvania and obtained the needed 270 Electoral College votes to win the presidency, despite the Trump campaign’s accusations of voter fraud and dozens of legal challenges in key states.

Andrew Harnik/AP

Transition begins

President-elect Joe Biden, accompanied by Vice President-elect Kamala Harris, speaks about economic ­recovery on Nov. 16 in Wilmington, Del. By early December, Biden had named key members of his administration’s economic team.