Formed February 2, 1864 (6th county)
Jefferson County (12,081), Boulder (1,201)
The unique red brick and stone courthouse with castle-like towers was built in 1888. It is located one a city block bounded by Washington, Third, Monroe, and Centennial Streets. Ornate wooded stairs climb the inside of the facility. Montana State Highway 69 is three blocks east of the building. John Paulsen provided the Richardsonian Romanesque designs. An Annex was added. Radersburg was the home for an earlier courthouse in 1865. Jefferson County was formed on February 2, 1864 as the 6th county. Boulder is named for local outcropping. The county was named after the third President of the United States, Thomas Jefferson.
Jefferson County government consists of a sheriff and 3 Commissioners. One District Court Judge serves Jefferson, Beaverhead, and Madison counties. The county is located in the southwest part of the state between Butte, Montana and Helena, Montana. The county center is 6.8 miles South-Southeast of Boulder. The county is surrounded clockwise by Lewis and Clark, Broadwater, Gallatin, Madison, Silver Bow, Deer Lodge, and Powell counties. The county is roughly the shape of the number 4. The Continental Divide makes up most of the west border. Two rivers form the south border. A mountain range is the north border. The east border is a straight line with a slight ledge at the southeast.
The area of the county is 1657 square miles. It is 42 out of 56 in the state. It ranks 16 out of 56 in population in the state. It has a density of 7.3 persons per square mile making it 11 out of 56 in the state. Jefferson County has 18.2% of its population in its incorporated areas. Interstate Highway 15 enters from the north and exits to the southwest. Interstate Highway 90 crosses the extreme south from east to west. United States Highway 287 cuts the southeast tip of the county from north to south. Boulder is in the north center of the county. Boulder is the county seat and the largest city. It is 9.9% of the county population. This county is in the Helena Micropolitan Statistical Area.
Boulder
Whitehall
