Ruth Cornelia Kelsey was born on 3 July 1894 in Ann Arbor, Michigan. She was the daughter of Francis W. Kelsey (1858-1927); Professor of Latin and Literature at the University of Michigan from 1889 until his death and President of the Archaeological Institute of America from 1907 to 1912. Ruth Kelsey graduated with a Bachelor of Arts degree from the University of Michigan in 1918. On 22 July 1918, Kelsey accepted an invitation from Edgar L. Hewett to serve as a fellow in Native American Art and Drama at the School of American Research. Kelsey relocated in San Diego, California where she was a librarian and also engaged in silver fox ranching. Kelsey and Fred Carl Diel were married on 17 July 1920. Patricia Ruth Diel Nichols was born to this marriage on 5 June 1934 in Van Nuys, California. The Diels moved later to Nevada and engaged in construction work.
From the guide to the Ruth Kelsey Diel Papers, 1918-1970, (Museum of New Mexico. Fray Angélico Chávez History Library.)
