The United States government collects and provides access to data on a wide range of topics. In addition to the decennial U.S. Census, which attempts to compile information about the entire U.S. population every ten years, the Census Bureau conducts a number of periodic surveys (most notably the American Community Survey) that provide additional information and context about the U.S. and its inhabitants. Additionally, individual agencies (like the C.D.C.) collect and disseminate data.
The following sites also contain information that can be helpful when researching demographic characteristics by ZIP code.
To search within a city's website for a topic, you can type your keywords into Google and then limit by domain.
For example, to find information on reopening during COVID-19 on the City of Boston's website, you might try typing into Google:
covid reopening site:boston.gov
Or, in North Adams:
covid reopening site:northadams-ma.gov
This will return results only from the web domain that you type in after site:
Would you like to see what a city's official COVID guidance looked like during the early days of the pandemic? The Internet Archive's Wayback Machine archives web pages regularly and lets you view older versions of them. Type or paste in a URL, and the Wayback Machine will return a calendar that shows when older versions of the page were archived. Just click on a date, then on a timestamp to see what the site looked like at that time.
If the URL is newer, you can try looking up the main city website in the Wayback Machine, choose a date, and then try navigating to the COVID page on the archived version of the site. (Warning: it can take a very long time for archived pages in the Wayback Machine to load.)