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 90 in New York
Interstate 90 (I-90) is a part of the Interstate Highway System that runs from Seattle, Washington, to Boston, Massachusetts. In the U.S. state of New York, I-90 extends from the Pennsylvania state line at Ripley to the Massachusetts state line at Canaan, and is the second-longest highway in the state after NY 17. Although most of the route is part of the tolled New York State Thruway, two non-tolled sections exist along I-90 (the first, situated outside of Buffalo, is included in the Thruway system; the second, situated in the Capital District, is not part of the Thruway system and links Albany and its eastern suburbs). Within New York, I-90 has a complete set of auxiliary Interstates, which means that there are interstates numbered I-190 through I-990 in the state, with no gaps in between. For most of its length in New York, I-90 runs parallel to the former Erie Canal route, New York State Route 5 (NY 5), U.S. Route 20 (US 20) and the CSX railroad mainline that traverses the state.