Halsey was a prolific author and editor. His original works included travel writing ("Two Months Abroad", collecting his reportage for the "Tribune" on the Paris World's Fair (1878)), New York State history ("" (1901), "The Pioneers of Unadilla Village, 1784-1840" (1902), and a number of articles), literary criticism ("Our Literary Deluge And Some of Its Deeper Waters" (1902)) and family history (extended introduction to "Thomas Halsey of Hertfordshire, England and Southampton, Long Island" (1895)).