Compiled By Markson Omagor
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.
At a White House news conference on Tuesday, Mr Trump, a Republican, described Ms Harris as “my number one draft pick”.
Ms Harris will debate Mr Trump’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 for a major party – Sarah Palin by the Republican party in 2008 and Geraldine Ferraro by the Democrats in 1984. Neither ended up on the winning ticket.
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 country’s finest public servants”.
He noted how she had worked closely with his late son, Beau, when she was California’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 I’m proud now to have her as my partner in this campaign.”
Ms Harris later tweeted that Mr Biden “can unify the American people because he’s spent his life fighting for us. And as president, he’ll build an America that lives up to our ideals.
“I’m honored to join him as our party’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 pledged in March to name a woman on the ticket. He had faced mounting calls to pick a black woman in recent months as the nation was convulsed by social unrest over 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 after failing in her bid to win the Democratic nomination.
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 nation’s preeminent historically black colleges and universities. She has described her time there as among the most formative experiences of her life.
Harris says she’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. I’m good with it. You might need to figure it out, but I’m fine with it,” she said.
ometimes the obvious pick is obvious for a reason. Kamala Harris was the front-runner to be Joe Biden’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.
She’s relatively young and telegenic, and as the daughter of Jamaican and Indian immigrants reflects the growing diversity of the Democratic Party.
What’s more, she’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 Biden’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, she’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.