Mildred Yates was born to Thomas A. C. Yates and Ocea Lee (Walters) Yates and grew up in Scott County, Kansas before attending Fort Hays State University and receiving a teaching certificate. Sometime afterwards, Harkness also attended Charlotte Murray Nursing School in Dodge City, Kansas. Before her retirement in 1982, Harkness worked in a variety of career fields in the Wichita County and Scott County, Kansas areas, including teaching, nursing, farming, auto sales, and the well-drilling business. After her retirement, Harkness moved to Lawrence, Kansas.

Throughout and after her professional career, Harkness was heavily involved in aging issues and aging advocacy. While living in Scott County, Harkness helped to build a VIP senior citizen center in Scott county and served within the Southwest Kansas Area Agency on Aging (SWKAAA) as a chairperson. Harkness helped to found the Kansas Coalition on Aging (KCOA), National Silver Haired Congress, and Kansas Silver Haired Council; and she planned for the development of the Kansas Department on Aging (KDOA). After the creation of the KDOA, Harkness also served on the department’s advisory board. While living in western Kansas, Harkness was a member on multiple committees within the Kansas Silver Haired Legislators organization, served as the director of the Western Kansas Transit Incorporated, as a delegate to the 1981 White House Conference on Aging (WHCA), and as a senior intern to Senator Bob Dole in 1981.

After her retirement and subsequent move to Lawrence, Kansas, Harkness was a member of the Lawrence/Douglas County Advocacy Council for Aging (DCACA) and the Kansans for the Improvement of Nursing Homes (KINH). Harkness was also elected to the KINH board of directors in 1988. Harkness served as a member of the American Association of Retired Persons (AARP) Douglas County chapter and the National AARP and was appointed to an advisory board within the Jayhawk Area Agency on Aging (JAAA). Harkness was also elected to the National Silver Haired Congress (NSHC) as a senator.

With her work in aging advocacy and senior issues, Harkness was also active in the Lawrence Chamber of Commerce and the Douglas County Republican Women's Club, as well as an active member of the Rebekah Lodge and the American Baptist Church. In 1938, Harkness married Leo Burton Harkness, who died sometime between the mid-1960s and the early 1970s. She remarried Raymond Harkness in 1972, who died in October 2000. Harkness had two children, Dr. E. Gail Harkness and Major D. W. Harkness, and one foster son, Vincente Goybuyan. Mildred Harkness died in 2004.

[Information retrieved from "Mildred Evelyn Harkness" obituary, Lawrence Journal World, November 29, 2004; Harkness' resume in accession file; and collection materials.]