[2] After graduating, Thornton attended the University of Pennsylvania, where he played football[3][page needed] and served as class president during his freshman year.

[10][page needed] Thornton was also named an officer of the Order of Leopold and a Companion of the Legion of Honor of France.

[11] In 1922 Thornton was named chairman of the board and president of the Canadian National Railways and tasked with modernizing and amalgamating several lines.

When the Conservative Party came to power in 1932, Thornton was forced to resign, denied a pension, and removed from the Board of Directors of a local bank.

He delivered commencement addresses at MIT and Syracuse and earned an honorary doctorate from his alma mater, the University of Pennsylvania.