Mary St. John was born in 1839 in Illinois to John St. John and Nancy Mary Foster. In 1861 she was married to Charles Morse. They had four children: Maud Evelyn Veronica (March 9, 1861), Cassius (1862), Mabel (1868), and Nellie (1873). She died on August 6, 1915 in Jo Daviess County. She was buried at Morseville Cemetery in Jo Daviess.