List of Interstate Highways
There are 70 primary Interstate Highways in the Interstate Highway System, a network of controlled-access freeways in the United States. They are assigned one- or two-digit route numbers, whereas their associated "auxiliary" Interstate Highways receive three-digit route numbers. Typically, odd-numbered Interstates run south-north, with lower numbers in the west and higher numbers in the east; even-numbered Interstates run west-east, with lower numbers in the south and higher numbers in the north. Highways whose route numbers are divisible by "5" usually represent major coast-to-coast or border-to-border routes (ex. I-10 travels from Santa Monica, California, to Jacksonville, Florida, traveling from the Pacific to Atlantic oceans). Additionally, auxiliary highways have their numbering system where a different number prefixes the number of its parent highway.
Oklahoma
Transportation in Oklahoma is generated by an anchor system of Interstate Highways, inter-city rail lines, airports, inland ports, and mass transit networks. Situated along an integral point in the United States Interstate network, Oklahoma contains three primary Interstate highways and four auxiliary Interstate Highways. In Oklahoma City, Interstate 35 intersects with Interstate 44 and Interstate 40, forming one of the most important intersections along the United States highway system.