James Fergus, an early pioneer from Scotland, moved to central Montana in 1880. In 1883, his half brother William Fergus joined him with his wife and nine kids. There were a handful of post offices in the area and William Fergus' started one near his ranch in 1899. He was the postmaster and Ellen Romunstad served as postmistress.

The town of Fergus was established when the Milwaukee Railroad built a branch line between Hilger and Roy; it was halfway between the family's two ranches. At one point the town had a grain elevator, a combined store/post office, a school, a church and a community hall.

In July of 1948 The Lewistown Daily News listed the population of Fergus at six people. The elevator was dismantled when the railroad abandoned the line in the late 1960s. Today a fading “F” scrolled in stone sits on the hillside above town.