Inter-American Highway, c.3,400 mi (5,470 km) long, section of the Pan-American Highway system from Nuevo Laredo, Mexico, to Panama City, Panama. Much of the highway prior to 1941 had been built by the countries concerned, but wartime necessity led the United States to appropriate funds to assist completion. Later work was done by each nation on its own. The highway includes alternate routes and makes use of existing local roads. It is virtually complete, and many sections have been upgraded and paved.