Marjory Casson was the daughter of a Scottish emigrant father, who died soon after she was born. As a child she lived with her mother on Selma Station near Bothwell, Tasmania. She was educated for a few years at the Friends' School in Hobart and later at the Advanced School in Adelaide, and lived at "Four Winds", 4 Woodleigh Road, Blackwood in 1913-14. She suffered from poor health.
She became an unofficial student of George Cockburn Henderson, Professor of Modern History and responsible also for English at the Adelaide University, and although she did not matriculate or graduate Henderson employed her to read essays and give tuition in English Literature.
She married the widower Frank Casson and moved to Loxton. Her writings on the history of Loxton, Loxton: District and Town,were later completed by W. R. C. Hirst and published in 1972.
After her husband died, she lived at Port Noarlunga (SA), in Tasmania, and then at Grange (SA). She was involved with the preservation of Capt. Charles Sturt's house, The Grange and wrote the pamphlet "The Story of Grange: the home of Capt. Charles Sturt" (1966). She served as a Public Examinations Board Public Examiner and did some tutoring in English.
Her memoir of George Cockburn Henderson was published in 1964, and she organised the contributing of the first microform reading equipment to the Henderson Room (main accommodation for research students in history at the University of Adelaide) as a memorial to him.
