Ok so Hawaii has one... What about Alaska? Oh wait, aside from a few sections of controlled access highway (in Anchorage, Wasilla, and Fairbanks), Alaska is expresswayless. Technically the roads are still funded through the interstate system, but they aren't exactly highways. From Wikipedia:
Currently, all Interstates in Alaska are unsigned [3] and are not generally referred to by their highway numbers. In fact most Alaskans are unaware of those numbers.
Most of the lengths of the Interstates in Alaska are not constructed to Interstate Highway standards, but are small, rural, two-lane, undivided highways. Title 23 provides that "Highways on the Interstate System in Alaska and Puerto Rico shall be designed in accordance with such geometric and construction standards as are adequate for current and probable future traffic demands and the needs of the locality of the highway."
Picture of an Alaskan Interstate: http://upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Glenn_Highway_and_Mount_Drum.jpg/800px-Glenn_Highway_and_Mount_Drum.jpg