I have most of the entire collection of hardback national geographics from 1930 to 1970. Wonder how legal it would be to scan them. Always wondered.
Good news: It's very likely that the copyright has expired. If you were to scan them, remember to upload them to archive.org for everyone else to see.
Bad news: It's only the case if the copyright hasn't been renewed by the owner. Usually most owners don't renew them, but to determine whether or not this is the case, you need to go through huge catalogs of registered entries from the U.S. copyright office.
Scanning typically falls under fair use, so copyright only applies to distribution of the scans.
edit: Maybe you edited or maybe I'm just dumb. Anyway, the problem with relying on a lack of renewal is that you have to prove a negative. NYPL among others have been doing interesting work on this problem: https://www.nypl.org/blog/2019/09/01/historical-copyright-re...
Once copyright has lapsed, it cannot be reinstated.
https://www.crummy.com/2019/07/22/0
https://www.nypl.org/blog/2019/05/31/us-copyright-history-19...
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Notes:
1. Technically, the obligation existed until the 1976 act, at which time copyright status was automatic, but was retroactively waived for works never having lapsed, back to 1964, in the 1992 act. It's complicated. (NYPL link above.)