Holger Cahill was born Sveinn Kristjan Bjarnarson in Iceland in a small valley near the Arctic Circle, on January 13, 1887. His parents, Bjorn Jonson and Vigdis Bjarnadottir, immigrated to the United States from Iceland sometime later in the 1880s. In 1904, his father deserted the family, forcing Sveinn to be separated from his mother and sister to work on a farm in North Dakota. He ran away and wandered from job to job until settling in an orphanage in western Canada, where he attended school and became a voracious reader.
As a young man, he worked at many different jobs and attended night school. While working on a freighter, he visited Hong Kong, beginning his life-long interest in the Orient. Returning to New York City, he eventually became a newspaper reporter, continued his studies at New York University, and changed his name to Edgar Holger Cahill. In 1919 he married Katherine Gridley of Detroit. Their daughter, Jane Ann, was born in 1922, but the couple divorced in 1927.
Cahill met John Sloan circa 1920, and they shared a residence. Cahill also wrote publicity (until 1928) for the Society of Independent Artists, through which he made many friends in the arts. From 1922 to 1931, he worked under John Cotton Dana at the Newark Museum, where he received his basic experience in museum work, organizing the first large exhibitions of folk art.
From 1932 to 1935, he was the director of exhibitions for the Museum of Modern Art. In 1935, Cahill was appointed director of the Works Progress/Projects Administration (WPA) Federal Art Project (FAP), until its end in June 1943. In 1938, Cahill organized a countrywide exhibition "American Art Today" for the New York World's Fair. He also married MoMa curator Dorothy Canning Miller in that year.
Profane Earth, Cahill's first novel, was published in 1927, followed by monographs on Pop Hart and Max Weber, miscellaneous short stories, and a biography of Frederick Townsend Ward, entitled A Yankee Adventurer: The Story of Ward and the Taiping Rebellion. Following the end of the Federal Art Project, Cahill wrote two novels, Look South to the Polar Star (1947) and The Shadow of My Hand (1956).
Holger Cahill died in Stockbridge, Massachusetts in July 1960.