Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
Note that even though the publisher's copyright was not renewed, a number of stories published in Amazing in 1941 had their copyrights renewed by their authors.
Captions
A Nazi submarine descends to the underwater city of Atlantis.