route 20 is an important east/west u.s. highway in the north part of the united states from newport, oregon to boston, massachusetts u.s. route 90 is an important east/west u.s. highway in the south part of the united states from van horn, texas to jacksonville beach, florida the dwight d. eisenhower national system of interstate and defense highways, commonly known as the interstate highway system, is a network of controlled-access highways that forms part of the national highway system in the united states. the system extends throughout the contiguous united states and has routes in hawaii, alaska, and puerto rico.