The item has no copyright marks on it as can be seen at links and original upload. At bottom left is a logo for Tooker Litho Company--they printed the poster--and the poster's order number. At Right is Litho in USA.
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 (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.