The Grammy Award winners sang on the West Front of the Capitol Building for the president, vice president, first family, Congress, Supreme Court Justices, cabinet members and a crowd of thousands on the National Mall.
Clarkson, the voice behind "Stronger," belted out '"My Country, 'Tis of Thee" following President Obama's second inaugural address on Monday.
"Wow," said Sen. Charles Schumer (D-N.Y.), chairman of the Joint Congressional Committee on Inaugural Ceremonies, after Clarkson's performance.
Beyonce, who sang for the Obamas' first inaugural dance four years ago, closed out the public ceremony with the "Star Spangled Banner." Both singers were accompanied by the United States Marine Band.