heavily forested mountain range of NE Oreg. & SE Wash.: highest peak, 9,105 ft (2,775 m)
Origin:
from their bluish appearance at a distance
See Blue Mountains in American Heritage Dictionary 4
A range of northeast Oregon and southeast Washington consisting of an uplifted, eroded part of the Columbia Plateau. It rises to 2,777.3 m (9,106 ft) at Rock Creek Butte in Oregon.
A range of eastern Jamaica rising to 2,252 m (7,388 ft) at Blue Mountain Peak. It is a coffee-growing area.