Williams, who played for nine presidents starting with Harry Truman, was 87.
He was known for his 1958 hit "Autumn Leaves." The song was the only instrumental to ever reach No. 1 on the Billboard pop charts
In 1966, he had another hit with "Born Free," the soundtrack to the movie of the same name.
Born Louis Wertz in Omaha, Neb., Williams started playing piano when he was just 3 years old. He eventually studied jazz at the Julliard School of Music in New York City before embarking on a concert career.
His other hits included "The Impossible Dream," "Yellow Bird" and "Theme from Somewhere in Time." Eventually, he recorded 18 gold or platinum albums.
Williams was also the first pianist to be honored with a star on the Hollywood Walk of Fame.
City News Service contributed to this report.