The IPass states include Delaware, Florida, Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, and West Virginia. Additionally, both I-PASS and E-ZPass are utilized in the province of Ontario, Canada.
I-PASS is part of the E-ZPass system and can be used whereever E-ZPass is accepted.
The E-ZPass New York website has a good map of the whole system.
The official IPASS brochure on using the IPASS in other states.
The I-Pass can be used in 18 states: Delaware, Florida, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Minnesota, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Virginia, and West Virginia.