Remember that ZIP codes were made to make mail delivery easier. They weren’t made to correspond to existing boundaries such as cities, counties, or even states. If it is more efficient for a mail carrier to drive across a state line to deliver mail, the ZIP code “boundary” will cross the state lines. ZIP codes don’t usually cross state lines, but some do (65733, 71749, and 73949 are good examples). The complete list of ZIP codes that cross state lines is available as part of our US ZIP code list.
