What is the longest highway in the United States?

The longest highway in the United States is U.S. Route 20 (US 20). Stretching from Boston, Massachusetts, to Newport, Oregon, it spans 3,365 miles (5,415 kilometers), making it the longest continuous highway in the U.S. US 20 travels through several states, passing through diverse landscapes, including mountains, plains, and farmlands. Along the route, travelers can visit major cities such as Chicago and Yellowstone National Park, and experience a wide range of cultural and natural landmarks.