Learn the history and meaning of usps postal codes, why it's called a ZIP code, whether a postal code is a ZIP code, and what ZIP code numbers stand for.

For some credit card purchases in Canada, a postal code is required as a security measure. If using a credit card in the U.S., you may need to use a ZIP code instead.

In the annual rankings of Realtor.com’s “hottest ZIP codes,” the 18104 ZIP code was ranked 10th in the Northeast, putting it in the honorable mention category for the national list.