Idora Smith, born August 25, 1865, was the eldest child of N.D. Smith, a farmer in Union Valley, Cortland County, New York. Other children in the family included Idora's brothers Clayton (b. 1873) and Warner (b. 1886), and sister, Rita, (b. 1887). In 1877 Idora wrote her first diary. That year she attended school on an irregular basis, as winter weather permitted and for three months in late summer. Her church attendance was on a regular basis; twice on Sundays and for special events during the week. The second diary was written in 1882, when Idora was seventeen, and she continued writing on a daily basis until her death in 1937.

In 1882 and 1883 she attended brief sessions at Cazenovia, a seminary in Cortland, to prepare her for teaching. Following that she taught in local rural schools for nineteen years. At the age of thirty-six, in 1901, Idora moved to Helena, Montana, to help her aunt, Mary Jane Haskell, in her boarding house located at 431 South Park. Within a few months Idora accepted a teaching assignment in Helena at $60.00 per month. She also taught in the Stearns area (near Wolf Creek) and in the Helena valley, living with her aunt and bicycling to school. In 19O3 Idora accepted a teaching position in Bald Butte, near Marysville. She met Herbert J. Guthrie, a native of Mumford, Wisconsin, who worked at a mine there. They were married on September 14, 1904, at her family home in New York and honeymooned at Niagara Falls. The couple returned to Montana and Herbert continued working at hard rock mining and locating placer ground to prospect. The Guthries set up cabins and moved from one location to another including Hope Gulch, Spring Gulch, and Bald Butte.

In 1907 the Guthries adopted a five-year old boy who was the son of a relative and named him Herbert Raymond Guthrie. Raymond lived in Helena all of his life, dying in 1963. Herbert's brother, Edmund D. Guthrie, also lived in Helena. Herbert Guthrie had frequent health and alcohol problems. Idora contributed to the family's livelihood by raising chickens and selling eggs, bread, and butter in the "mill" community. During the years 1914 through 1916 Herbert decided to try his hand at homesteading. The family built a homestead cabin near Bald Butte and bought horses, cattle, pigs, and chickens. Idora helped with farm chores, continued to work at the placer sites, and carried out all of the domestic duties including tutoring Raymond, washing, cooking, baking, milking, mending, and sewing. She was also a devoted letter writer, read books and papers from her home town, played cards, and took the train to Helena to attend church and Eastern Star meetings.

In 1917 Herbert was hospitalized in Helena and diagnosed as tubercular. The family moved to a house at 534 Highland, and the homestead and placer ground were leased for three years. Idora returned to her family home in Cortland in 192O, to be with her widowed mother, and remained there for six years. Raymond remained in Helena. Though her mother died in 1924, Idora stayed in New York and took a nursing care course and contracted to be a representative to sell Fifth Avenue Fashions door-to-door. She was able to support herself in this way for the remainder of her life. In 1926 Idora returned to Helena to care for Herbert who was seriously ill. He died on December 18, 1926, at the age of sixty-one. Idora remained in Helena earning her living selling women's and children's fashions and by renting apartments in her home. In October 1937 she was hospitalized with diabetes; she died on December 31.