Incorrect. It is almost certainly still in copyright in the United States. Anything published after 1925 will be in copyright except for those published without notice 1926-1977 or were not renewed 1926-1963. The exceptions almost certainly don't apply to NatGeo.
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...
Under US law, between 1925 and 1964, it was necessary to renew copyright every 28 years.[1] There are many works which have fallen out of copyright for nonrenewal, and there are projects which are now going through copyright renewal records to determine which of these are in fact now public domain in the US. Roughly 3/4 of potentially copyrighted works (published since 1924 and initially registered) have proved to be public domain.
Once copyright has lapsed, it cannot be reinstated.
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.)
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...