When Gertrude M. Stegmaier was born on 23 December 1878, in Eagle Lake, Blue Earth, Minnesota, United States, her father, Joseph C. Stegmaier, was 29 and her mother, Johanna Zech, was 31. She married John F. Sullivan on 14 May 1906, in Madison Lake, Blue Earth, Minnesota, United States. They were the parents of at least 1 son and 2 daughters. She lived in Hamilton, Skagit, Washington, United States in 1910 and Waterville, Le Sueur, Minnesota, United States in 1940. She died on 22 January 1960, in Madison Lake, Blue Earth, Minnesota, United States, at the age of 81, and was buried in Calvary Cemetery, Madison Lake, Blue Earth, Minnesota, United States.