The Blue Mountains are located
largely in northeastern Oregon
but also extend into southeastern Washington. The range lies east and southeast of Pendleton, Oregon and extends to the Snake River along the Oregon-Idaho border.
Geologically, the range is a part of the larger rugged Columbia River Plateau, located in the dry area of Oregon east of the Cascade Range. The highest peaks in the range include the Elkhorn Mountains at 2,776 m, Strawberry Mountain at 2,755 m, and Mount Ireland at 2,531 m.The nearby Wallowa Mountains, east of the main range near the Snake River, are considered a subrange of the Blue Mountains.
The flora of the Blue Mountains reflects a drier climate with more temperature extremes compared with the Cascade Range. The Blue Mountains are transitional between the coastal ranges and the Rocky Mountains with plants found in the Blue Mountains such as Clematis columbiana and Eritrichium nanum that are normally considered species characteristic of the Rockies.