After graduating university, Mason began a career in Chicago's newspaper industry. He began working at the
Chicago Record-Herald in 1902. After a brief stint working at the
Chicago Tribune, he began working at the
Chicago Evening Post. He was the
Evening Post's managing editor from 1916 until 1922. In 1922, Mason left Chicago to take a job in
New York City as the managing editor of the
New-York Tribune. He continued as editor after it became the
New York Herald Tribune following a 1924 merger with
The New York Herald. He left in 1926 to become the editor in chief of the
New York Evening Post, holding this role until 1933 when the newspaper was sold to
J. David Stern. ==Later political and writing careers==