As part of our continuing series Only in New Hampshire, we're answering questions posed by Granite Staters about their communities. Producer Hannah McCarthy answered this one:
Samer asks: "Why is there no exit 21 on I-93 North?"
When Hannah spoke to the Department of Transportation and asked why the exit numbers on I-93 North jump from 20 to 22, she received a pretty quick and easy answer. Back in the 1960s, there was a plan to connect Franklin, New Hampshire to I-93. This junction would have happened at Exit 21, so the number was reserved while they held hearings about the project since other construction was underway. Exit 22 was built with the assumption that an Exit 21 would eventually come to pass, but the project was never approved.
It turns out, this is not an uncommon phenomenon. The Federal Highway Administration has been asking states for years to convert their consecutively numbered exits to mileage-based exits. And for the most part, states have managed to comply, but New Hampshire is one of the few hold outs.
Changing a state's highway exit numbers so they all line up with mile markers is an expensive task for the state and a confusing transition for travelers. So for now at least, New Hampshire will continue to have consecutively numbered exits, and a missing Exit 21.