The term CITY ON THE OREGON TRAIL can be solved by two crossword solutions: BOISE (5 letters) and BOISEIDAHO (10 letters). Boise is the capital and most populous city of the U.S. state of Idaho. It is located on the Boise River in southwestern Idaho, in the heart of the Treasure Valley. Boise is the principal city of the Boise City-Nampa metropolitan area and is the largest city between Salt Lake City and Portland, Oregon. Boise was a major stop along the Oregon Trail, which ran through the city in the mid-1800s.