 Allen was born on May 13, 1900 or 1907, in Atlantic, Iowa, the son of Thomas Allen of Missouri and Lillian M. Allen of Potosi, Wisconsin.He attended public schools in Iowa and Nebraska, where he studied civil engineering, and completed courses in engineering science and war training at the University of Southern California and Caltech.He was married to Margaret Sachs or Margaret H. Rogers of Detmold, Germany; they had a son, Don A. Allen, Jr.