The Philadelphia Inquirer reported that she wanted to make something quick that used ingredients that homes usually had in the pantries.
Campbell calls Reilly's creation "the mother of all comfort foods."
She left the company in 1961 and eventually came back as manager of Campbell's Kitchen in 1981, according to the company. Reilly finally retired in 1988.
Her original recipe for the Thanksgiving staple was been donated to the National Inventors Hall of Fame in 2002, the company said.