the longest us interstate is
Interstate 90, Chicago, IL. The Chicago Skyway is a 7.8 mile toll bridge connecting downtown Chicago with East Chicago, IN. For the longest time, since the bridge was opened in 1958, it was considered to be part of I-90 â the longest Interstate highway in the United States. In 1999, however, the city of Chicago discovered in looking through its old records that it was never technically approved as an Interstate highway.