Zip Code

A ZIP Code (an acronym for Zone Improvement Plan[1]) is a system of postal codes used by the United States Postal Service (USPS). The term ZIP was chosen to suggest that the mail travels more efficiently and quickly[2] (zipping along) when senders use the code in the postal address... Because ZIP Codes are intended for efficient postal delivery, there are unusual cases where a ZIP Code crosses state boundaries. https://en.wikipedia.org/wiki/ZIP_Code

Stop Using Zip Codes for Geospatial Analysis. You can also use Census units such as a Census Block Group or Census Tract. As I mentioned it has not always been easy to find and collect this data at scale but there are many new tools that are becoming available to use. CenPy is a Python library that allows you to connect and find Census data (good tutorial here) where you can find measures from the decennial census or American Community Survey.

• If your data is sensitive, strip all the attributes out except for the address and a serial integer to use as an ID, and after geocoding you can associate the results back to your original data using that ID. The Census Geocoder is free, requires no log in, allows you to do batches of 1,000 addresses at a time, and forces you to use these safety precautions. For bigger jobs, there’s an API.
• see also https://geomap.ffiec.gov/ffiecgeomap/