US Highway System
You could think that US Highway System is an obsolete with the Interstate System. But especially in the Midwest and the South, a lot of the roads are designated US Highways rather then state highways.
Not that there is much of a difference, many US Highways are two-lanes at-grade and are maintained by state DOTs. In recent decades, funding is not based on US Highway designation but another set of designations on whether or not a road is an arterial highway. California and New York have a notable lack of US Highways.
