Bynum is an unincorporated community and census-designated place in Teton County, Montana, United States, about 13 miles north of Choteau. Its population was 31 as of the 2010 census.Bynum is the site of a one-room country school, a general store, post office, an agate shop, and Two Medicine Dinosaur Center, which provides displays and educational programs about dinosaurs.The town's name is derived from name of a family of early settlers in the area. The post office was established in 1885. In 1908 work on the Bynum Reservoir began.