Interstates with No Auxiliary Routes by FlaxmanR

Question 11

This interstate currently runs in two sections: the longer of the two runs between Interstates 76 and 80 in central Pennsylvania and is eventually intended to connect with the shorter of the two, which runs from the Pennsylvania border to the delightfully named town of Painted Post in New York. What interstate is the bane of numbering purists, as it lies between Interstates 79 and 81 but has a number well outside of them, breaking the convention of north-south interstate numbers getting progressively larger from west to east?