When Mary Elliott was born on 4 February 1885, in Elkhart, Polk, Iowa, United States, her father, Francis Marion Elliott, was 27 and her mother, Margaret Jane Law, was 24. She married Andrew Johnson on 16 February 1910, in Cambridge, Story, Iowa, United States. They were the parents of at least 2 sons. She lived in Emmet Township, Emmet, Iowa, United States in 1925 and Armstrong Grove Township, Emmet, Iowa, United States for about 10 years. She died on 20 March 1964, in Estherville, Emmet, Iowa, United States, at the age of 79, and was buried in Armstrong, Emmet, Iowa, United States.