When William McDonald Thomas was born on 30 October 1913, in Manassa, Conejos, Colorado, United States, his father, William Montgomery Thomas, was 26 and his mother, Marguerite Jane McDonald, was 25. He married Jennie Louise Ricottone on 12 June 1938, in Aguilar, Las Animas, Colorado, United States. He lived in Antonito, Conejos, Colorado, United States in 1930 and Alamosa, Alamosa, Colorado, United States in 1940. He died on 8 August 1992, in Denver, Colorado, United States, at the age of 78, and was buried in Fort Logan National Cemetery, Denver, Colorado, United States.