There are multiple zip codes in my state (Massachusetts) that cover multiple towns some examples include 01002 which is Pelham and much of Amherst, 01027 which is both Easthampton and Westhampton (different towns) etc.

Thanks for the heads up. It definitely used to include the 0xxxx ZIP codes. It is supposed to just naively fetch everything between 00000 and 99999 and record the USPS response. I'll have to re-run it and update it.