Dunn began his career with Christian Brothers College (CBC) of the St. Louis Municipal League, the city's de facto second division.
CBC won the league title, but Dunn moved to the Missouri Athletic Club for the 1915–1916 season.
In May 1920, Ben Millers won the National Challenge Cup over Fore River of the Southern New England Soccer League.
In its place, they competed in what they called the American Professional Soccer Championship which pitted the champions of the two leagues.
[2] Ben Millers repeated as league champion in each of the next two seasons and finished runner-up to Bethlehem Steel in the 1926 National Challenge Cup.