Secrets are for private notebooks. If you want to store secrets in public notebook stake a look at https://observablehq.com/@endpointservices/public-api-keys

Interesting, thanks for the comment! It's worth noting that with Wolfram Alpha, the app ID isn't really super sensitive: the worst that can happen is someone grabbing it and using some of your quota, which is unlikely since it's much easier to sign up and get your own ID. What I do is make an unlisted wrapper library (as described here) and just write my app ID there and don't really care if it's technically exposed.

That said I do wish Observable supported fully private libraries for this use case!

Cool - thanks for sharing! You might be interested in this notebook, that accesses Wolfram data in an entirely different way: https://observablehq.com/@mcmcclur/city_data-from-wolfram-research

Nice, thanks for sharing! Is there something you think could be generalised and a good addition to the simple API + demos that are already included here? I'm not so familiar with all the other Wolfram offering.

Yes, it can certainly be generalized. Here's a completely different example illustrating the vibrational modes of a region specified by the user: https://observablehq.com/d/6039661965abff13 Essentially, any function that you might write in Mathematica can be deployed to the Wolfram Cloud and accessed via an API call. It's quite different from the WolframAlpha API, though; it complements it the stuff here, rather than adding to it.