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Boulder, Montana
Jefferson County Courthouse in Boulder
Jefferson County Courthouse in Boulder
Location of Boulder, Montana
Location of Boulder, Montana
Boulder, Montana is located in Montana
Boulder, Montana
Boulder, Montana
Location in Montana
Country United States
State Montana
County Jefferson
 • Town 1.12 sq mi (2.91 km2)
 • Land 1.12 sq mi (2.91 km2)
 • Water 0.00 sq mi (0.00 km2)
4,990 ft (1,521 m)
 • Town 1,201
 • Density 1,072.32/sq mi (412.71/km2)
 • Metro
Time zone UTC-7 (MST)
 • Summer (DST) UTC-6 (MDT)
Area code(s) 406
FIPS code 30-08575
GNIS feature ID 0780250

Boulder is a town in and the county seat of Jefferson County, Montana, United States. It is on the north bank of the Boulder River between Butte and Helena, slightly east of the Continental Divide, at the intersection of Interstate 15 and Montana Highway 69. The population was 1,201 at the 2020 census. It is part of the Helena Micropolitan Statistical Area, which includes all of Lewis and Clark and Jefferson counties; its population is 83,058 according to the 2020 Census.

Established in the 19th century as a stagecoach station, Boulder grew into a regional trading center for farmers, ranchers, and miners and, by the end of that century, home to state schools for the deaf, blind and developmentally disabled. In the 21st century, it is the center of government in Jefferson County, and institutions based in the town offer services for disabled adults and troubled youths. Its library system serves about 10,000 people, and its high school district covers more than 1,000 square miles (2,600 km²). Three buildings in Boulder are listed on the National Register of Historic Places.


Named for the many large boulders in the vicinity, the town of Boulder Valley was established in the early 1860s as a stagecoach station on the route between Fort Benton and Virginia City. It later became a trading center for nearby agricultural areas and the Elkhorn, Comet, and Baltimore mining districts. The Great Northern Railway branch line from Helena to Butte reached Boulder in 1888. State schools for the deaf, blind, and developmentally disabled were established in the city in 1892. In 1897, the town's name was shortened to Boulder.

Geography and geology

Boulder as seen from near Interstate 15

Boulder lies at an elevation of 4,990 feet (1,521 m) above sea level along Interstate 15 at its intersection with Montana Highway 69, about 35 miles (56 km) north of Butte, and 27 miles (43 km) south of Helena. The town is on the north bank of the Boulder River, a tributary of the Jefferson River. According to the United States Census Bureau, the city has a total area of 1.13 square miles (2.93 km2), all of it land.

In the late Cretaceous Period (roughly 81 to 74 million years ago), molten rock (magma) rose to the Earth's surface in and near what later became Jefferson County and eventually formed an intrusive body of granitic rock up to 10 miles (16 km) thick and 100 miles (161 km) in diameter. This body, known as the Boulder Batholith, extends from Helena to Butte, and is the host rock for the many valuable ores mined in the region. As the granite cooled, it cracked, and hot solutions filled the cracks and formed mineral veins bearing gold and other metals. Millions of years later, weathering allowed gold in the veins to wash down to the gravels in the Boulder River valley. The Boulder mining district was essentially limited to placer mining of those gravels, because the source lodes were in other mining districts in the mountains.


Historical population
Census Pop.
1880 214
1920 682
1930 926 35.8%
1940 510 −44.9%
1950 1,017 99.4%
1960 1,394 37.1%
1970 1,342 −3.7%
1980 1,441 7.4%
1990 1,316 −8.7%
2000 1,300 −1.2%
2010 1,183 −9.0%
2020 1,201 1.5%
U.S. Decennial Census

2010 census

As of the census of 2010, there were 1,183 people, 514 households, and 298 families residing in the city. The population density was 1,046.9 inhabitants per square mile (404.2/km2). There were 565 housing units at an average density of 500.0 per square mile (193.1/km2). The racial makeup of the city was 93.6% White, 1.8% Native American, 0.4% Asian, 0.3% from other races, and 3.9% from two or more races. Hispanic or Latino of any race were 2.9% of the population.

There were 514 households, of which 23.2% had children under the age of 18 living with them, 42.8% were married couples living together, 9.1% had a female householder with no husband present, 6.0% had a male householder with no wife present, and 42.0% were non-families. 37.9% of all households were made up of individuals, and 11.5% had someone living alone who was 65 years of age or older. The average household size was 2.15 and the average family size was 2.79.

The median age in the city was 43.7 years. 18.9% of residents were under the age of 18; 9.3% were between the ages of 18 and 24; 23.5% were from 25 to 44; 34.8% were from 45 to 64; and 13.6% were 65 years of age or older. The gender makeup of the city was 52.4% male and 47.6% female.

Arts and culture

Boulder Community Library is the center of a library system serving about 10,000 people in Jefferson County, Montana. In 2005, it had about 39,000 books and serial volumes in its collection, 85 subscriptions, 3,200 videos, 1,500 audio materials, and 21 Internet terminals.

Boulder has three buildings on the National Register of Historic Places. The Jefferson County Courthouse, on Centennial Avenue, was added in 1980. The Montana Deaf and Dumb Asylum, also known as the Old Administration Building, off Montana Highway 69 (formerly Montana Secondary Highway 281) near Boulder, was added in 1985. The Boulder Hot Springs Hotel, southeast of Boulder on Montana Highway 69, was added in 1979.

Two weekly newspapers, The Boulder Monitor and The Jefferson County Courier are published in Boulder. A low-power radio station, KEME, 106.3 FM, owned by Jefferson County Disaster and Emergency Services, broadcasts from Boulder. A licensed FM radio translator, K296AN, owned by the Boulder TV Association, also broadcasts from Boulder.

Boulder's Elkhorn Treatment Center, which operates under the Montana Department of Corrections, is known for its work with women battling methamphetamine addiction.


The average temperature in January is 20 °F (−7 °C), and in July it is 64 °F (18 °C). Annual snowfall averages 33 inches (84 cm).

Climate data for Boulder, Montana
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Average high °F (°C) 33
Average low °F (°C) 9
Precipitation inches (mm) 0.5


About 300 people are employed in Boulder at the Montana Developmental Center, a state institution for people with developmental disabilities. Another 100 or so people work for Alternative Youth Adventures (Youth Dynamics, Inc.), which provides residential services for troubled youth. In addition, Riverside Corrections, a state-run detention center for juvenile females, employs about 30 people.

Boulder and vicinity are home to commercial "health mines" for which it is claimed by testimonial that exposure to radon gas mitigates auto-immune diseases such as arthritis. Though contributing to the economy of the area by attracting tourists, the practice is controversial because of the "well-documented ill effects of high-dose radiation on the body."


Jefferson High School in Boulder is part of Jefferson High School District #1, covering about 1,100 sq mi (2,800 km2) in the northern half of Jefferson County. The district, based in Boulder, draws students from Basin, Clancy, Jefferson City and Montana City in addition to Boulder. About 280 students in grades 9 through 12 enrolled at the high school in 2007. The school had about 20 teachers and a student-teacher ratio of about 14 to 1. The district also serves students in Basin Elementary District 5, Boulder Elementary District 7, Clancy Elementary District 1, and Montana City Elementary District 27.

The town is served by Boulder Community Library.

See also

Kids robot.svg In Spanish: Boulder (Montana) para niños

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