Montague's upbringing in the natural beauty of her native White Sulphur Springs strongly influenced her writing. Her literary works often captured the essence of mountain life, with novels and stories set primarily in West Virginia. The Sowing of Alderson Cree (1907) is a novel set against the backdrop of a West Virginia feud. Montague's later works such as In Calvert's Valley (1908), Linda (1912), and Deep Channel (1923) offer deep character studies of mountain folk. In addition, her personal interest in the students at what's now known as the state Schools for the Deaf and the Blind in Romney prompted her to write Closed Doors (1915).

A notable theme in Montague's work was her engagement with disability. She struggled with visual impairments such as night blindness, tunnel vision, and cataracts and portrayed characters with similar challenges. In the 1920s, Montague introduced the mythical lumberman Tony Beaver in stories like "Up Eel River" (1923) and "The Today Tomorrow" (1923). Tony, a larger-than-life figure in the mold of Paul Bunyan, embodies the rugged, resourceful spirit of the West Virginia logging camps.

Although much of Montague's work was centered around the mountains, she did venture into broader themes, such as in England to America (written about World War I), which earned the O. Henry Award in 1919 and garnered praise from President Woodrow Wilson. The story was lauded for its plea for a league of nations, marking a shift from her typical Appalachian settings to global themes.