Mary Kavanaugh Oldham was born in Madison County, Kentucky and raised in that state. She worked as a schoolteacher until age 28, when she married James Philip Eagle, later the governor of Arkansas, in 1882. Mary Kavanaugh Oldham Eagle supported her husband's political career and accompanied him throughout the state on his campaigns. In addition, she was an active campaigner for women's right to vote. She founded the Women’s Cooperative Association and was a prominent figure in the Arkansas Federation of Women’s Clubs. She was the author of The Congress of Women: Held in the Woman’s Building, World’s Columbian Exposition, Chicago, USA (1894). Her younger brother Kie Oldham was James Philip Eagle's private secretary while he was governor. Their brother William Kavanaugh Oldham served as acting governor of Arkansas for six days in 1913.