What unique borders did the United States gain when it acquired the territory from the Mexican Cession

they gained California which is next to the pacific ocean we now have "from sea to shining sea".

`stare decisis is a legal doctrine that obligates courts to follow historical cases when making a ruling on a similar current or future case. stare decisis ensures that cases with identical facts be approached in the same way, unless overruled by the same court or a higher court such as the us supreme court. simply put, it binds courts to follow legal precedents set by previous decisions.

stare decisis is a latin term meaning "to stand by that which is decided".

the answer to your question is

the treaty of hopewell