Missoula (mĭzōˈlə) [key], city (1990 pop. 42,918), seat of Missoula co., W Mont., on the Clark Fork of the Columbia River; inc. 1889. In the midst of five watered valleys, large forests, and an extensive dairy and cattle area, Missoula is a commercial center with lumber and paper, printing and publishing, food, chemicals, construction materials, furniture, and fabricated metal products industries, but the Univ. of Montana is the largest employer. The (Peace) Treaty of Hell Gate in 1855 between the warring Salish and Blackfoot tribes opened the area to settlement. Hell Gate town was founded nearby in 1860 and moved to the Missoula site six years later. The coming (1883, 1908) of the railroads stimulated Missoula's growth. A regional headquarters of the U.S. Forest Service, including the Smokejumper Center, and an art museum are located in the city.