In addition to the county maps showing cities and townships announced previously, now you can also view an interactive ZIP Code map of every U.S. County, found in the Reference Maps menu.
As an example, here is a ZIP Code map of Auglaize County, Ohio:

As shown in the above example, if a ZIP Code area falls completely OR partially within the county, it will get included on the map.
If you then want to see all of the ZIP Codes in the surrounding counties and states too, just click anywhere outside the county or search for a new place using the Search places
box above the map.
Of course you can also just use the ZIP Codes map tool to see all U.S. ZIP Codes. On that tool, you can try out the Colorize ZIPs
button on the left side to apply colors to the ZIP Code map.
I hope you find these useful additions to the growing set of State- and County-based interactive Reference Maps, as well as the listing of all Townships and Ranges in the U.S.
Bonus for reading this far: If you want to create custom maps based on groups of ZIP Codes, be sure and try out the mapBuilder tool found just below most map tools on the website! On the go? Quickly find out what ZIP Code area you are currently in (based on your device location) using the What ZIP Code Am I In? tool, found in the Current Location Tools menu.
Happy mapping!