U.S. Route 3 (US 3) is a United States Numbered Highway running 277.90 miles (447.24 km) from Cambridge, Massachusetts, through New Hampshire, to the Canada–United States border near Third Connecticut Lake, where it connects to Quebec Route 257.
Signage on US Route 3, approaching the intersection with Interstate 495 and Massachusetts Route 110 in Chelmsford
US 3 in Lincoln, New Hampshire
US 3 Bus. sign
United States Numbered Highway System
The United States Numbered Highway System is an integrated network of roads and highways numbered within a nationwide grid in the contiguous United States. As the designation and numbering of these highways were coordinated among the states, they are sometimes called Federal Highways, but the roadways were built and have always been maintained by state or local governments since their initial designation in 1926.
The "final" U.S. Highway plan as approved November 11, 1926
This sign, photographed in 1941 on US 99 between Seattle, Washington, and Portland, Oregon, illustrates one rationale for a federal highway system: national defense.