Marjory Rose Casson (nee Walker) was born in Adelaide, on 14 April 1889 to William Walker, a young Scotsman from Stirlingshire who died of tuberculosis when she was eleven months and Annie Welch a first generation Australian. She and her mother moved to Selma Station, near Bothwell in Tasmania. Selma Station was run by Mrs Honoria McRae, Marjory's mother's aunt, and her two bachelor sons, James and Duncan McRae. From 1913 to 1914, Casson lived at 'Four Winds', 4 Woodleigh Road, Blackwood.

Casson's was educated at the Friends' School in Hobart and later at the Advanced School for Girls, Adelaide. Casson's poor health led her to become an unofficial pupil of George Cockburn Henderson, Professor of Modern History who was also responsible for English at the University of Adelaide. Casson neither matriculated nor graduated, but Henderson was so impressed with her that, when it first became possible for him to have a tutorial assistant, he engaged Marjory Walker to read essays and to give tuition in English literature. Casson later married a widower, Frank Casson, the father of her student, a Professor at the University of Cape Town. The Cassons moved to Loxton, the place of Frank's business. Mrs Casson later wrote the early part of a history of Loxton which has now been completed for publication by Mrs WRC Hirst of the University of Adelaide.

After her husband's death, Mrs Casson lived for a time at Port Noarlunga and in Tasmania before returning to settle in Adelaide. Many interests and activities occupied her later years. She was involved in the preservation of Captain Charles Sturt's house and was for the rest of her life a member of the Trust, she was employed as a Public Examinations Board examiner in English, she wrote an unpublished history of 'Tasmania's Aboriginal People' and did some general research on Tasmania's history. In 1961 she raised money from Professor Henderson's pupils and friends to purchase the first microfilm reading equipment for the University of Adelaide in his memory. The room in which the equipment was stored was named after Henderson. Mrs Casson wrote a memoir of Henderson, published first in 'South Australiana' in March 1964 and then separately by the Libraries Board of South Australia. She was a lover of literature and contributed articles to newspapers and magazines, wrote poetry and talked on Australian Broadcasting Corporation radio. Mrs Casson died on 25 June 1965.