Interstate 305

Unsigned and doesn't even have a legislative (state) numbering. It was used for Business Interstate 80 in Sacramento for the sole sake of getting federal funds from AASHTO. The 5.3 mile long route was added to the Interstate system in May, 1980, as a result of I-80/I-880 changes in Sacramento in 1979-80.

Planned 3.3 mile spur route from I-5 in Salem, OR. The freeway was proposed in the mid 70's, but was withdrawn in 1977 or 1978. The current route that takes its place is Business route 99E. I-305 shows up on the 1985 Rand McNally atlas, although it currently doesn't exist.