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.
Interstate Highway System
Typically, lower limits are established in Northeastern and coastal states, while higher speed limits are established in inland states west of the Mississippi River. For example, the maximum speed limit is in northern Maine, varies between from southern Maine to New Jersey, and is in New York City and the District of Columbia. Currently, rural speed limits elsewhere generally range from . Several portions of various highways such as I-10 and I-20 in rural western Texas, I-80 in Nevada between Fernley and Winnemuca (except around Lovelock) and portions of I-15, I-70, I-80, and I-84 in Utah have a speed limit of . Other interstate highways in Idaho, Montana, South Dakota and Wyoming also have the same high speed limits.