Joe Biden on January 20 became the 46th president of the United States with a call to unity, vowing to bridge deep divides and defeat domestic extremism two weeks after a mob attack tried to undo his election victory. On a frigid but sunny day at the very Capitol building that was assaulted on January 6, Biden swore the oath of office moments after Kamala Harris, who became America's first woman vice president. "Democracy is precious, democracy is fragile and at this hour, my friends, democracy has prevailed," Biden said before a National Mall. Kamala Harris made history on January 20 when she was sworn in as Joe Biden's vice president, becoming the first woman, the first Black American and the first Asian American to hold the second-highest US office. Moments after her swearing-in, she tweeted "Ready to serve".