How many interstates are there in the USA?
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.
List of highways in Puerto Rico
Puerto Rico has of Interstate highways. There are three designated Interstate Highways in Puerto Rico. As with Interstate Highways in Alaska and Interstate Highways in Hawaii, these routes do not connect to the rest of the United States Interstate Highway System, but still receive funding in a similar fashion to the Interstates in the contiguous US.