Boulder is a city located in Jefferson County Montana. It is also the county seat of Jefferson County. With a 2020 population of 1,298, it is the 50th largest city in Montana and the 9252nd largest city in the United States . Boulder is currently growing at a rate of 0.85% annually and its population has increased by 9.72% since the most recent census, which recorded a population of 1,183 in 2010. Boulder reached it's highest population of 1,298 in 2021. Spanning over 1 miles, Boulder has a population density of 1,155 people per square mile.
The average household income in Boulder is $52,567 with a poverty rate of 20.64%. The median rental costs in recent years comes to $612 per month, and the median house value is $139,100. The median age in Boulder is 49 years, 49.2 years for males, and 47.3 years for females.