Boulder is a town located in the state of Montana in the United States. It serves as the county seat for Jefferson County and is situated on the north bank of the Boulder River. Geographically, the town is positioned between Butte and Helena, just east of the Continental Divide at the intersection of Interstate 15 and Montana Highway 69.
As of the 2020 census, the population of Boulder was 1,201. The town is included within the Helena Micropolitan Statistical Area, which encompasses both Lewis and Clark and Jefferson counties.