Robert Bruce Harley was born in 1918 in Minnesota. In 1940 he graduated with a bachelor’s degree in history from William Penn University and a year later with a master’s degree from Haverford College in Pennsylvania. He served in the U.S. Army from 1941-1945 in Great Britain, North Africa, and Italy as a combat engineer, landing craft engineer, and a heavy cargo truck driver. He resumed his graduate studies at the University of Iowa, graduating in 1948 with a doctorate, specializing in American colonial history. He taught at Western Illinois University for 11 years during which time he met and married Clara Horcasitas of New Mexico. In 1959 he was employed by the U.S. Air Force serving mostly at March Air Force Base in Riverside, California but also in Germany. In 1983 he transitioned from the Air Force to become the first archivist for the Catholic Diocese of San Bernardino until 1998. He died in Redlands, California in 2008 and was buried in the Riverside National Cemetery.

Many of his manuscripts were published as stand-alone articles in various publications and/or formed part of the twelve volume Readings in Diocesan Heritage or the single volume The Story of Agua Mansa: Its Settlement, Churches, and People.