The date of Monica Shannon's birth is not documented. In an autobiographical sketch in The Junior Book of Authors, she says she was born in March but neglects to mention the year. Some sources speculate that she was born about 1905, but that date is inconsistent with both her own accounts of her childhood and the known dates of her employment at the Los Angeles Public Library (1916-1925). This information makes it unlikely that she was born later than 1900 and it suggests that probably she was born a year or two earlier.

Shannon was born in Belleville, Ontario, Canada, but she is considered an American author because her family moved to the United States when she was about six months old. After living briefly in Seattle, they moved to the Bitter Root Valley in the Montana Rockies, where Shannon's father operated a thoroughbred stock ranch...