Dallas was born in Invercargill, the daughter of Frank and Minnie Mumford. She became blind in one eye at 15, then spent three years at the Southland Technical College and was engaged at 19. But her fiance broke off the engagement to serve in Great Britain during World War II. During the war she worked at an army office and as a milk tester. Following the war, her works of poetry, Mountain Mornings was published in The Southland Times. She adopted her maternal grandmother's name, Dallas, as a pen name. Her first book of poetry, Country Road was published in 1953. In 1954 she moved to Dunedin, where she lived for most of her life.
Her poetry was influenced by William Wordsworth and the southern New Zealand landscape. Two of her most notable pieces of poetry, "Photographs of Pioneer Woman" and "Pioneer Woman with Ferrets" were both written to show the inequality and sexist stereotypes of the time and to also give these pioneer women a voice. She was awarded the 1968 Robert Burns Fellowship by the University of Otago, which she used to launch a series of children's books, beginning with The Children in the Bush. In 1977, she was a joint winner of the New Zealand Book Award for Poetry for her collection "Walking on the Snow"; that same year she received for "Song for a Guitar and Other Songs" the Buckland Literary Award, for "the Literary Work for the year of the highest Literary Merit". In 1978 the University of Otago made her an honorary Doctor of Literature. Later, as her eyesight deteriorated, she received A Blind Achievers' Award. In 1989, she was appointed a Commander of the Order of the British Empire for services to literature.
- The Joy of a Ming Vase (2006)
- Curved Horizon: An Autobiography (1995)
- Collected Poems (1987)
- Steps of the Sun (1979)
- Song for a Guitar (1976)
- Walking on the Snow (1976)
- The Children in the Bush (1969)
- Ragamuffin Scarecrow (1969)
- Shadow Show (1968)
- Day Book: Poems of a Year (1966)
- Experiment in Form (1964)
- The Turning Wheel (1961)
- Country Road and Other Poems (1953)
- Mountain Mornings (1946)
- Room, Adrian (2010). Dictionary of Pseudonyms: 13,000 Assumed Names and Their Origins (5th ed.). McFarland. p. 130. ISBN 0-7864-4373-1.
- "Ruth Dallas 1919–2008; Southland poet saw meaning in landscapes". The Southland Times. Retrieved 28 January 2011.
- Willhardt, Mark; Parker, Alan Michael (2000). Who's who in twentieth-century world poetry. Psychology Press. p. 76. ISBN 0-415-16355-2.
- International Who's Who in Poetry (12th ed.). Taylor & Francis US. 2004. p. 233. ISBN 1-85743-178-2.
- "Cemeteries search". Dunedin City Council. Retrieved 29 November 2014.