Questions about Public Domain

[Kid Charlemagne]

The smart-aleck answer is "anything before Steamboat Willie."

 

[S'mon]

Snopes has a good summary.

Seems fairly simple - it has a copyright date of 1935, so under the US's insane 95 year "Mickey Mouse" term for publisher-owned works, it is currently due to expire in 2030. Of course Congress has been effectively (& Unconstitutionally) creating an unlimited copyright term by extending copyright faster than works fall into the PD, so in actuality its term of protection is indefinite.

Edit: The UK's current life +70 years "dead German poets" copyright term is also insane IMO.