Ruth Edna De Velde was born in 1909 in the Chicago area, and grew up in Chicago suburbs, including Wheaton, Illinois. Her father was a high school teacher in Irving Park. Being concerned about providing a Christian education for their two children (her older brother was Everett C. De Velde), her parents decided to move to Wheaton in 1923, in time for her brother to enter Wheaton College. Ruth attended Wheaton Academy.

Ruth went on to attend Wheaton College herself (1927-1931), and met her future husband there (Lyndon Roth Hess). They shared a common calling to serve on the mission field as teachers of missionary children, and were married in August, 1932, before sailing for Africa in November.

They were sent out to Sakeji School in Northern Rhodesia (now Zambia), under the auspices of the Brethren Assemblies (Plymouth Brethren). Mr. Hess began as a teacher, but assumed the duties of principal when the British missionary who had held that position went back to England. Ruth Hess also began as a full-time teacher but, during their second year at Sakeji, she took on the responsibilities of the school's housekeeper. She continued to teach on a part-time basis.

The Hesses had five children, and served at Sakeji School until 1975, when Mr. Hess resigned because of a suspected heart problem. Following a furlough in the United States, when the condition was discovered not to be serious, they returned to Sakeji, becoming involved with direct ministry to the Lunda Tribe.

The Hesses retired in 1982 and lived in Wheaton until they moved to Grand Rapids, Michigan in 1994 where Ruth died on March 4, 1997.