Idaho is a landlocked state in the Mountain West subregion of the United States. It shares a small portion of the Canada–United States border to the north, with the province of British Columbia. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington and Oregon to the west. The state's capital and largest city is Boise. With an area of 83,569 square miles (216,440 km2), Idaho is the 14th largest state by land area. With a population of approximately 1.8 million, it ranks as the 13th least populous and the 7th least densely populated of the 50 U.S. states.

Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington state to distinguish it from the national capital, both named for George Washington. Washington borders the Pacific Ocean to the west, Oregon to the south, Idaho to the east, and the Canadian province of British Columbia to the north. The state was formed from the western part of the Washington Territory, which was ceded by the British Empire in the Oregon Treaty of 1846. It was admitted to the Union as the 42nd state in 1889. Olympia is the state capital, and the most populous city is Seattle.