Hapgood worked as the drama critic of the New York City Commercial Advertiser and of the Bookman in 1897–1902.

[citation needed] He inspired T. G. Masaryk to write the first memorandum to president Wilson for independence of Czechoslovakia from London to Washington in January 1917.

[3] In this capacity Hapgood helped advance the agenda of President Woodrow Wilson, who sought the establishment of such a body at the Paris Peace Conference of 1919.

In 1919 President Wilson appointed Hapgood Minister to Denmark, in which post he served for about six months.

His first wife, Emilie Bigelow Hapgood, whom he married in 1896, went on to become famous in her own right as a theatrical producer in New York.