In 1912, he joined the Vitagraph film company, becoming its leading man in the 1910s, Williams was voted America's number one star in 1915, starting his career on stage as a teenager, the year he made perhaps his most popular film of all, The Juggernaut. Vitagraph wrecked a real train in this action melodrama, which co-starred Williams with his most frequent leading lady, Anita Stewart. They were also teamed in the studio's earliest and perhaps most famous entry in the then-popular serial genre, The Goddess in 1915, and Williams made a dashing gentleman thief in Vitagraph's 1917 version of the ever popular Arsene Lupin. He continued his popularity streak into the 1920s, often portraying stalwart military heroes.