Grant was born Ruth Siddons in Morrisonville, Clinton County, New York, USA, on 25 February 1909. Her parents were Frank J. Siddons (1879–1978) and Susan Bates Siddons (1882–1973). She had one older sister, Inez Sanders (1907–2002). At some point, she visited Cuba along with her sister.

Grant graduated from Plattsburgh State University, became a teacher, and taught in Sullivan County. She eventually became the secretary for the Superintendent of Liberty Schools, retiring in 1970.

In 1936, she married Howard Newton Grant (1909–1974). The couple had two sons. Her husband was also a teacher. One of her hobbies was playing tennis.

Grant died in Liberty, Sullivan County, New York, USA on 1 May 2020 at the age of 111 years, 66 days.