To determine a city's postal code, access the website of the United States Postal Service or use another relevant website, such as Zip-codes.com. Alternatively, contact USPS via phone.
Upon accessing the USPS website, enter the name of the city and state in the appropriate boxes and click on Find. If known, also enter the street address along with the company name to get a more accurate search result.
Similarly, enter the city's name and state in the Find ZIP Codes of a City section on Zip-codes.com and click on Find ZIP codes. This leads to a list of ZIP codes in the city.
Alternatively, call USPS using the toll-free number, 1-800-ASK-USPS, between 8 a.m. and 8:30 p.m. EST from Monday to Friday and between 8 a.m. and 6 p.m. on Saturdays to know the city's postal code over phone, as of July 2015.