Montague’s upbringing in White Sulphur Springs shaped her writing, with many works set in West Virginia. Her novel The Sowing of Alderson Cree (1907) explores a local feud, while later works like In Calvert's Valley (1908) and Linda (1912) focus on character studies of mountain people. Her interest in students at the state Schools for the Deaf and Blind in Romney led to Closed Doors (1915).

A key theme in her writing was people with disabilities, reflecting her own struggles with visual impairments. In the 1920s, she introduced the mythical lumberman Tony Beaver, reminiscent of Paul Bunyan, in stories like "Up Eel River" (1923).

Though focused on mountain life, Montague also addressed broader themes, as in England to America, a World War I story that won the O. Henry Award in 1919 and earned praise from President Wilson for its plea for a league of nations.