Standing alongside his wife Jill, the 77-year-old then presented a wreath of white roses at Delaware's War Memorial Plaza, before observing a moment of silence to commemorate the military personnel who fought in World War Two and the Korean War.
On Tuesday, US President Donald Trumpmocked a White House correspondent for wearing a mask to a press briefing.
Since the coronavirus pandemic forced Americans into their homes in March, the Democratic presidential hopeful has been campaigning virtually from home.
"Presidents lead by example, and wearing a mask helps protect others", TJ Ducklo, a Biden campaign spokesman, said.
The video begins with a clip of Biden's controversial "ain't black" comments, which made headlines last week which the former Vice President has since apologized.
In other news, Twitter has added a fact-checking alert to a tweet issued by Trump regarding mail-in ballots. "That's not going to increase the likelihood that people are going to be better off".
Trump retweeted a message that showed an AFP picture of Biden in his mask and sunglasses with commentary that mocked the look, even as Trump's own government advises wearing masks to slow the virus's spread.
When asked why he wasn't wearing one, the president claimed Ford officials had told him that wearing a mask was "not necessary" at that moment.
"You know, as vain as Donald Trump is - I mean, think of what he goes to her every day to prepare himself to be seen, you know". I wasn't criticizing him at all. "Why would I ever do a thing like that?"
As part of the same exchange at the White House event, the president asked Reuters' Jeff Mason to remove his mask as part of the Q&A.
"The guidance is recommended but not required", McEnany said.
"It is a bit peculiar", McEnany said. "That in his basement, right next to his wife, he's not wearing a mask". But he's wearing one outdoors when he's socially distant. "So I think that there was a discrepancy there".
Kyoto Animation comments on suspect's arrest
Media reports at the time said Aoba told police he had taken the action because the studio had plagiarized his novel. Many others tried but failed to escape to the roof, fire officials said and many died of carbon monoxide poisoning .
Key ruling expected in Huawei CFO Meng's US extradition case
Canadian Prime Minister Justin Trudeau said Tuesday his government should not have to explain any court decision to China. He lamented last week that communist-led China "doesn't seem to understand" the meaning of an independent judiciary.