Also known occasionally as Harold McGrath, he was born in Syracuse, New York. As a young man, he worked as a reporter and columnist for the Syracuse Herald newspaper until the late 1890s when he published his first novel, a romance titled Arms and the Woman. According to the New York Times, his next book, The Puppet Crown, was the No.7 bestselling book in the United States for all of 1901. MacGrath subsequently wrote novels for the mass market about love, adventure, mystery, spies, and the like at an average rate of more than one a year. He would have three more of his books that were among the top ten bestselling books of the year. At the same time, he published a number of short stories for major American magazines such as The Saturday Evening Post, Ladies Home Journal, and Red Book magazine. Several of MacGrath's novels were serialized in these magazines and contributing to them was something he would continue to do until his death in 1932. In 1912, Harold MacGrath became one of the first nationally known authors to write directly for the movies when he was hired by the American Film Company to do the screenplay for a short film in the Western genre titled The Vengeance That Failed. MacGrath had eighteen of his forty novels and three of his short stories made into films plus he wrote the story for another four movies. Three of his books were also made into Broadway plays. One of the films made from MacGrath's writings was the 1913 serialThe Adventures of Kathlyn featuring Kathlyn Williams. While writing the thirteen episodes he simultaneously wrote the book that was published immediately after the December 29, 1913, premiere of the first episode of the serial so as to be in book stores during the screening of the entire thirteen episodes. Among the movies made from MacGrath's short stories was the 1920 Douglas Fairbanks Production Company's feature-length adventure filmThe Mollycoddle, based on MacGrath's short story with the same title that appeared in The Saturday Evening Post in 1913. Directed by Victor Fleming, it featured Fairbanks, Ruth Renick, and Wallace Beery and was distributed by the newly created company United Artists. It is said that during this same time, a young Boris Karloff, who previously had a few uncredited movie roles, chose his stage name for his first screen credit during 1920 from the MacGrath novel The Drums of Jeopardy, which had also been published by The Saturday Evening Post in January of that year and which featured a Russian mad scientist character named Boris Karlov. The name Boris Karlov was used from MacGrath's book for the 1922 Broadway play, but by 1923 with actor Boris Karloff using the similar-sounding variation, the character for the first film version was renamed Gregor Karlov. Harold MacGrath's success made him a wealthy man and, although he traveled the world extensively, Syracuse, New York, was his home, and it was there during 1912 that he built an English country-style mansion renowned for its landscaped gardens. In an article in the April 23, 1932, issue of The Saturday Evening Post with the title "The Short Autobiography of a Deaf Man", MacGrath told the public how he had struggled early in life as a result of a hearing impairment. At a time in history when deaf people were typically considered as lacking intellectual acuity, he had concealed this from his employer and others. Harold MacGrath died at his home in Syracuse a few months after the article was published.
Funeral
Hundreds of people passed by the author's bier as his body lay in state in St. Paul's Episcopal Church in Syracuse, New York, before a 2 p.m. service on November 5, 1932. Rev. Dr. Henry H. Hadley, rector of St. Paul's, officiated at the church service.
