Numbered highways in the United States

Highways in the United States are split into at least four different types of systems, Interstate Highways, U.S. Highways, state highways, and county highways. Highways are generally organized by a route number or letter. These designations are generally displayed along the route by means of a highway shield. Each system has its own unique shield design that will allow quick identification to which system the route belongs. Below is a list of the different highway shields used throughout the United States.

Interstate Highways

Interstate Highway shields
Interstate 90 route marker
Standard Interstate
Interstate 476 route marker
Standard Interstate, wide
Interstate 80 (Iowa) route marker
California- and Iowa-style Interstate
Business Loop 19 route marker
Business Loop
Business Spur 44 route marker
Business Spur

The Interstate Highway System is a federally funded and administered (but state-maintained) system of freeways that forms the transportation backbone of the U.S., with millions of Americans relying on it for commutes and freight transport daily. Interstate highways are all constructed to precise standards, designed to maximize high-speed travel safety and efficiency. Interstate Highways also contain auxiliary routes, which are normally assigned a three-digit route number. All Interstate Highways are part of the National Highway System, a network of highways deemed essential to the defense, economy, and mobility of the country.