Garrison was named for William Lloyd Garrison by a Yankee veteran from the Civil War who had come for the gold rush and settled in the valley. Legend says he named the community after the man he most admired. The first post office was established in 1883 with William Facer as postmaster.
Garrison is located in southwestern Montana, between Helena, Butte and Missoula at the junction of I-90 and U.S. Highway 12.