Interstate 40.

“…In the Federal-Aid Highway Act of 1944, the Congress acted on these recommendations. The act called for designation of a National System of Interstate Highways, to include up to 40,000 miles “… so located, as to connect by routes, direct as practical, the principal metropolitan areas, cities, and industrial centers, to serve the National Defense, and to connect at suitable points, routes of continental importance in the Dominion of Canada and the Republic of Mexico.” https://www.fhwa.dot.gov/programadmin/interstate.cfm