Which state was populated by the expanse of the Oregon Trail, which can also be found in the Palouse region of the United States?
Palouse:  It is a major agricultural area, primarily producing wheat and legumes. Situated about 160 mi north of the Oregon Trail, the region experienced rapid growth in the late 19th century and was once Washington's most populous region, surpassing even the Puget Sound area. Oregon Trail:  The western half of the trail spanned most of the future states of Idaho and Oregon.
Washington