Bitterroot, river, c.120 mi (190 km) long, rising in SW Mont. and flowing north to join the Clark Fork River near Missoula. A Roman Catholic mission was established on the river in 1841, and missionaries are credited with introducing farming in the area. The Bitterroot Valley experienced rapid population growth in the 1990s.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.