The item has no copyright markings on it as can be seen in the links above. At bottom left is Litho in USA and some numbers which probably pertain to the print job for the poster. At bottom right are more numbers which probably are related to the printing of the poster, Tooker Litho Co., NY--they printed the poster.
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.