versatile American author noted especially for histories and historical fiction about the southwestern United States.

Horgan moved with his family to New Mexico in 1915 and studied at New Mexico Military Institute from 1920 to 1923. After spending the next three years working for the Eastman Theater in Rochester, N.Y., Horgan returned to the Military Institute, where he worked as a librarian until 1942. His career as a novelist began with the publication of the satirical novel The Fault of Angels (1933), about a Russian emigré's attempt to bring high culture to an American city. His trilogy Mountain Standard Time (1962), consisting of Main Line West (1936), Far From Cibola (1938), and The Common Heart (1942), depicts life in the Southwest in the early 1900s. A Distant Trumpet (1960) concerns late-19th-century soldiers who fought the Apaches. His short stories are collected in The Return of the Weed (1936), Figures in a Landscape (1940), and The Peach Stone (1967).

In addition to novels Horgan wrote historical sketches and books that sympathetically depict the Native American, Spanish, Mexican, and Anglo-American frontier cultures of the Southwest. Both his two-volume Great River: The Rio Grande in North American History (1954) and the biography Lamy of Santa Fe (1975) won Pulitzer Prizes for history. He also produced poetry, drama, and children's books.