The Salmon River, also known as "The River of No Return", is a river located in the U.S. state of Idaho in the western United States. It flows for 425 miles (685 km) through central Idaho, draining a rugged, thinly populated watershed of 14,000 square miles (36,000 km2). The river drops more than 7,000 feet (2,100 m) from its headwaters, near Galena Summit above the Sawtooth Valley in the Sawtooth National Recreation Area, to its confluence with the Snake River. Measured at White Bird, its average discharge is 11,060 cubic feet per second. The Salmon River is the longest undammed river in the contiguous United States.

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.