English: 1939, per the copyright notice. Note that the film itself premiered March 1940. The poster was likely published in late 1939 to promote the film's coming release.

English: Scan via Heritage Auctions.

English: "© 1939 by United Artists Corporation."

English: The poster included a valid copyright notice, seen at bottom left. However, the copyright for the artwork was not renewed, as was required by American copyright law to extend/maintain protection for works published 1963 or earlier. In order to maintain copyright protection, the poster would have had to be renewed 28 years after publication, in either 1966 or 1967 (see the sections for "Artwork: Original registrations and renewals" and refer to the links to search the copyright catalogs for those years). Because it was not renewed, copyright lapsed at that time. Note that the poster art is a distinct work from the film it represents and had to be renewed separately.