The Umatilla National Forest, in the Blue Mountains of northeast Oregon and southeast Washington, covers an area of 1.4 million acres (5,700 km2). In descending order of land area the forest is located in parts of Umatilla, Grant, Columbia, Morrow, Wallowa, Union, Garfield, Asotin, Wheeler, and Walla Walla counties. More than three-quarters of the forest lies in the state of Oregon. Forest headquarters are located in Pendleton, Oregon. There are local ranger district offices in Heppner and Ukiah in Oregon, and in Pomeroy and Walla Walla in Washington.

The Blue Mountains are a mountain range in the northwestern United States, located largely in northeastern Oregon and stretching into extreme southeastern Washington. The range has an area of about 15,000 square miles (39,000 km2), stretching east and southeast of Pendleton, Oregon, to the Snake River along the Oregon–Idaho border.