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.
Per The Portal to Texas History, this map is in the public domain. It was created in 1938 by Andrew Jackson Houston (who died in 1941) and published the same year (by Anson Jones Press). Registration was not renewed, per the Copyright Renewal database at Stanford University [1]archive copy at the Wayback Machine.
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