Wisconsin's governor Tony Evers has certified Joe Biden's election win in the key swing state. Recounts in the state's two largest counties yesterday confirmed the Democrat won by more than 20,000 votes.
Earlier, Arizona also certified its election results in favour of the Democrat.
"We do elections well here in Arizona. The system is strong and that's why I bragged on it so much," said Governor Doug Ducey, a Republican.
The US Electoral College, which selects presidents based on state-by-state vote totals, meets on 14 December.
Mr Biden beat White House Republican incumbent Donald Trump by 306 electors to 232, a margin the US president described as a "landslide" when it was to his benefit in 2016.
Also today it was revealed that the 78-year-old US president-elect has a foot fracture and will likely have to wear a medical boot. Mr Biden's team said he was taken to the doctor after he slipped while playing with his dog on Saturday.
"Get well soon!" Mr Trump said on Twitter, in a retweet of an NBC video showing Mr Biden leaving an orthopaedic office.
Joe Biden has formally picked ex-Federal Reserve chair Janet Yellen to lead the Treasury, one of a slate of economic officials who will break racial and gender barriers in the next US government.
Finance Minister Paschal Donohoe congratulated her on Twitter.
Congratulations to @JanetYellen on her nomination as US Treasury Secretary. I look forward to working closely together on global economic issues, as we embark on rebuilding and revitalising our economies after the #COVID19 pandemic.#G7 #Eurogroup https://t.co/Bv065osQdj— Paschal Donohoe (@Paschald) November 30, 2020
If she secures Senate approval, Ms Yellen would be the first female Treasury secretary, and be joined in the executive branch by the first African Americans to serve as her deputy - Nigerian-born Wally Adeyemo - and as head of the White House economic council - Cecilia Rouse.
"We face great challenges as a country right now. To recover, we must restore the American dream - a society where each person can rise to their potential and dream even bigger for their children," Ms Yellen tweeted following the announcement.
"As Treasury Secretary, I will work every day towards rebuilding that dream for all."
Mr Biden has also announced an all-female senior White House communications team, in what his office called a first in the country's history.
Among those named was Jen Psaki, who will serve in the highly visible role of White House press secretary.
Ms Psaki, 41, has held a number of senior positions, including White House communications director for the Barack Obama-Biden administration.
Honored to work again for @JoeBiden, a man I worked on behalf of during the Obama-Biden Admin as he helped lead economic recovery, rebuilt our relationships with partners (turns out good practice) and injected empathy and humanity into nearly every meeting I sat in.— Jen Psaki (@jrpsaki) November 29, 2020
Elizabeth Alexander was named communications director for incoming First Lady Jill Biden.
The appointments do not require Senate confirmation unlike most cabinet-level positions.
Meanwhile President Trump's administration will wage its last major policy fight before the Supreme Court as it seeks to exclude undocumented immigrants from the population count used to determine states' representation in Congress.