Highway 20

Highway 20 crosses the Snake River at Nyssa, Oregon, with Highway 26, and together they proceed through Parma and Caldwell, where they cross Interstate 84, and on to Boise. After Boise, Highway 20 coincides with Interstate 84 until Mountain Home, where it turns northwest by itself.

It passes the connection to Sun Valley and the edge of Craters of the Moon National Monument before reaching Arco. From Arco, it proceeds east to Idaho Falls and from there northeast to the entrance to Yellowstone National Park.