Visit the USPS website to access the USPS ZIP code directory online. Click the link that reads Look Up a ZIP Code, then search by address or city to find the desired ZIP code.
To search for a ZIP code by address, enter the street address, city and state, then click Find. To find all the ZIP codes in a particular city, leave the street address field blank, entering only the city and state, then click Find. For example, entering "Manhattan, NY" returns a list of all 106 different ZIP codes found in Manhattan.
Select the Cities by ZIP Code tab to get a list of all the cities or neighborhoods in a ZIP Code. For example, a search for ZIP code 10001 yields a list of 10 names, including New York, New York, which is the default city name; Empire State, New York; Manhattan, New York; Greeley Square, New York; and New York City, New York. Use the default or recognized city names to minimize delivery delays. Search a specific street address to find the ZIP+4 Code. Using the additional four digits after the traditional ZIP code is optional, but it reduces the amount of handling and the potential for error and misdelivery, says the U.S. Postal Service.