Idaho's largest city is Boise, which has five 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 foothills of the Rocky Mountains. The population of Boise was estimated to be 228, 790 in 2019, making it the third-largest city in the Northwest United States. Boise is the economic and cultural center of the Boise City-Nampa metropolitan area, which is home to around 700, 000 people. Boise is known for its vibrant downtown, outdoor activities, and cultural attractions.