After the Senate on Monday voted tremendously to confirm her nomination, Yellen was sworn in Tuesday as Treasury secretary by the nation's first female Vice President Kamala Harris at the White House, facing the Treasury building.
Yellen to be the first woman to lead the US Treasury Department, US President Joe Biden chose a progressive economist focused on unemployment who supports fiscal stimulus and tackling climate change.
The 74-year-old has made history before when she became the first female head of the Federal Reserve, the world's most powerful central bank, in 2014, and previously as head of the White House Council of Economic Advisors.
Her new role puts her at the centre of the ongoing storm battering the United States economy, which has seen a record slowdown in annualized growth and tens of millions of layoffs as it grapples with the world's largest coronavirus outbreak.
Yellen will take the lead in the effort to win Congressional support for Biden's proposed USD1.9 trillion economic rescue plan, and increasing the federal minimum wage to USD15 an hour.
In a note to Treasury staff, she praised their effort during the 2008 global financial crisis, saying they "helped save the economy from its worst crisis since the Depression. "Now we need to do it again," Yellen said.