Located in southwestern Montana, Jefferson County is Montana's 19th most populous with 10,049 residents, according to the 2000 Census.
Boulder, the county seat, is the state's 49th largest city with a population of 1,300. According to the Montana Almanac, by authors Andrea Merrill and Judy Jacobson, it was one of the original nine counties of the Montana Territory and holds the Jefferson River, named by explorers Lewis and Clark for President Thomas Jefferson. The county was established in 1865.
According to the U.S. Bureau of the Census, estimated median income for Jefferson County households in 1997 was $41,820. The county is 1,658.9 square miles in area: 1,656.7 square miles in land area and 2.2 in inland water area.
County residents experience the four distinct seasons. According to the Great Falls Weather Service, the average daily low in Boulder in January between 1961 and 1990 was 9.2 degrees above zero. The average daily high in July was 82.7 degrees above. The annual precipitation during the same period was 11.31 inches and the growing season was from May 8 to Sept. 30.
