Democratic presidential candidate Joe Biden has named Senator Kamala Harris as his running mate - the first black woman and Asian American in the role.
Once a rival for the top job, the California senator of Indian-Jamaican heritage had long been considered the front-runner for the number two slot.
The former California attorney general has been urging police reform amid nationwide anti-racism protests.
Mr Biden will face President Donald Trump in the election on 3 November.
Ms Harris will debate Mr Trumpâ€™s running mate, Vice-President Mike Pence, on 7 October in Salt Lake City, Utah.
Only two other women have been nominated as vice-presidential candidates - Sarah Palin by the Republican party in 2008 and Geraldine Ferraro by the Democrats in 1984. Neither made it to the White House.
A woman of colour has never been appointed to a presidential ticket by either of the two main American political parties. No woman has won the US presidency either.
What did Biden and Harris say?
Mr Biden tweeted that he had “the great honour” to name Ms Harris as his number two.
He described her as “a fearless fighter for the little guy, and one of the countryâ€™s finest public servants”.
He noted how she had worked closely with his late son, Beau, when she was Californiaâ€™s attorney general.
“I watched as they took on the big banks, lifted up working people, and protected women and kids from abuse,” he tweeted.
“I was proud then, and Iâ€™m proud now to have her as my partner in thisÂ campaign.”
Ms Harris later tweeted that Mr Biden “can unify the American people because heâ€™s spent his life fighting for us. And as president, heâ€™ll build an America that lives up to our ideals.
“Iâ€™m honored to join him as our partyâ€™s nominee for Vice President, and do what it takes to make him our Commander-in-Chief.”
The campaign announced that Mr Biden and Ms Harris will deliver remarks in Wilmington, Delaware, on Wednesday afternoon on “working together to restore the soul of the nation and fight for working families to move the country forward”.
Mr Biden had faced mounting calls to pick a black woman as his running mate in recent months as the nation was convulsed by social unrest over racial injustice and police brutality against African Americans, a key voting bloc to the Democratic Party.
Who is Kamala Harris?
Ms Harris, 55, dropped out of the presidential race in December.
She repeatedly clashed with Mr Biden during the primary election debates, most notably criticising his praise for the “civil” working relationship he had with former senators who favoured racial segregation.
The Democrat was born in Oakland, California, to two immigrant parents: an Indian-born mother and Jamaican-born father.
She went on to attend Howard University, one of the nationâ€™s preeminent historically black colleges and universities. She has described her time there as among the most formative experiences of her life.
Ms Harris says sheâ€™s always been comfortable with her identity and simply describes herself as “an American”.
In 2019, she told the Washington Post that politicians should not have to fit into compartments because of their colour or background. “My point was: I am who I am. Iâ€™m good with it. You might need to figure it out, but Iâ€™m fine with it,” she said.
The obvious pick
Sometimes the obvious pick is obvious for a reason. Kamala Harris was the front-runner to be Joe Bidenâ€™s running mate pretty much since the moment the presumptive Democratic nominee announced in March that he would pick a woman to be his ticket.
Sheâ€™s relatively young and telegenic, and as the daughter of Jamaican and Indian immigrants reflects the growing diversity of the Democratic Party.
Whatâ€™s more, sheâ€™s been in the spotlight of the national media, having campaigned for president in 2019 and, for a while last summer, risen to near the top of some polls. Many of her rivals for the number-two spot had never faced such scrutiny, so there was no proof that they could hold up under fire.
Another underrated advantage for Ms Harris was her friendship with Mr Bidenâ€™s late son, Beau, formed when they were both attorneys general. Mr Biden places a high value on family - and that connection may have made choosing her easier.
Now Ms Harris will have a chance to hit the campaign trail again and prove that she deserves this historic pick. If she succeeds, sheâ€™ll be in prime position to seek the presidency again, perhaps as early as 2024. Today has made her a force in the Democratic Party for years to come.
What is her record?
After four years at Howard, Ms Harris went on to earn her law degree at the University of California, Hastings, and began her career in the Alameda County District Attorneyâ€™s Office.
She became the district attorney - the top prosecutor - for San Francisco in 2003, before being elected the first woman and the first African American to serve as Californiaâ€™s attorney general, the top lawyer and law enforcement official in Americaâ€™s most populous state.
In her nearly two terms in office as attorney general, Ms Harris gained a reputation as one of the Democratic partyâ€™s rising stars, using this momentum to propel her election as Californiaâ€™s junior US senator in 2017. She was only the second black woman ever elected to that chamber.
She launched her candidacy for president to a crowd of more than 20,000 in Oakland at the beginning of last year.
But the senator failed to articulate a clear rationale for her campaign, and gave muddled answers to questions in key policy areas like healthcare.
She was also unable to capitalise on the clear high point of her candidacy: debate performances that showed off her prosecutorial skills, often placing Mr Biden in the line of attack.
The self-described “progressive prosecutor” tried to emphasise more left-leaning parts of her legacy - requiring body cameras for some special agents at the California Department of Justice, the first state agency to adopt them, and launching a database that provided public access to crime statistics, though she failed to gain traction.
“Kamala is a cop” became a common refrain on the campaign trail, spoiling her attempts to win over the more liberal Democratic base during the primaries. Those same law enforcement credentials could, however, prove beneficial in the general election when Democrats need to win over more moderate voters and independents.
Whatâ€™s the reaction?
The Trump campaign said the choice of running mate was proof that Mr Biden is “an empty shell being filled with the extreme agenda of the radicals on the left”.
“Not long ago, Kamala Harris called Joe Biden a racist and asked for an apology she never received,” the campaign said.
“Clearly, Phony Kamala will abandon her own morals, as well as try to bury her record as a prosecutor, in order to appease the anti-police extremists controlling the Democrat Party.
“In her failed attempt at running for president, Kamala Harris gleefully embraced the leftâ€™s radical manifesto, calling for trillions of dollars in new taxes and backing Bernie Sandersâ€™ government takeover of healthcare.”
Earlier on Tuesday, President Trump said in an interview with Fox Sports Radio that some men might feel “insulted” by Mr Bidenâ€™s commitment to pick a woman as his vice-presidential candidate.
Mr Biden pledged in March to name a woman on the ticket.
Former US President Barack Obama - whom Mr Biden served as vice-president for eight years - tweeted: “She is more than prepared for the job. Sheâ€™s spent her career defending our Constitution and fighting for folks who need a fair shake.
“This is a good day for our country. Now letâ€™s go win this thing.”
Susan Rice, the Obama-era White House national security adviser who was also on the vice-presidential shortlist, was among the first to congratulate Ms Harris.
“Senator Harris is a tenacious and trailblazing leader who will make a great partner on the campaign trail,” said the former diplomat.
“I am confident that Biden-Harris will prove to be a winning ticket.”