Mary Lou Cooley, 93, passed away peacefully on Nov. 9, 2020, at Harbor Healthcare & Rehabilitation Center in Lewes, Del.

Born in Washington, D.C., she graduated from Central High School and did secretarial work. She married her high school sweetheart, Neil W. Cooley, and graduated from Maryland University with a bachelor’s degree. She went on to work for the Smithsonian Institute in the National History building, as a scientific illustrator, before retiring to Delaware.

Cooley was preceded in death by her husband of 68 years, Neil W. Cooley; mother, Mary E. Sill; father, Charles Mainhall; and beloved brother, Robert Mainhall. She is survived by her children, Thomas Cooley and his wife, Betsey, Debbie McNally and her husband, Michael, Patti Brittingham, and Jamie Cooley and wife, Gail; 14 grandchildren and their spouses; and 34 great-grandchildren.

A Mass of Christian Burial was to be held Nov. 16, 2020, at St. Ann Catholic Church in Bethany Beach, Del., with interment at the Delaware Veterans Memorial Cemetery in Millsboro, Del. In lieu of flowers, the family requested memorial donations to the Alzheimer’s Association, c/o Seniors Helping Seniors; 26279 Bayside Dr.; Long Neck, DE 19966, or to St. Ann Catholic Church; 691 Garfield Pkwy.; Bethany Beach, DE 19930. Condolences can be sent online at