He was the co-owner of the Mount Royal Arena and founder of the New York Americans and Boston Bruins of the National Hockey League (NHL).

When unsuccessful, he turned his sights southwards and obtained options for NHL franchises in the United States (where the league was looking to expand to thwart competition), selling one franchise to Boston grocery magnate Charles F. Adams and keeping another for himself (financed by bootlegger Bill Dwyer) to play in New York's Madison Square Garden.

[2] Coincidentally, Duggan died shortly after being interviewed about the sudden death of Paddy Harmon, the builder of Chicago Stadium and another failed NHL aspirant.

Although Duggan was an important pioneer in the expansion of professional hockey in the United States, his legacy has often been overlooked in favour of other men like Tommy Gorman, Tex Rickard and Bill Dwyer.

As Baz O'Meara wrote in the Montreal Daily Star: "Essentially a pioneer and trustful to an unusual degree, he lost a considerable portion of the fruits of his vision.