This is the only treaty signed in 1790 that I can find. In no way does it pertain to this because Mexico didn’t even exist then.
August 7, 1790 Secret articles of US/Creek Treaty of 07/04/1790.
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This treaty discusses the continuance of U.S. trade with the Creek Nation in the event of war with Spain. McGillivray is appointed U.S. agent to the Creek Nation. U.S. agrees to educate and clothe a number of Creek children not to exceed four.
Treaties galore........ but not what is being hunted for as far as I can tell
http://en.wikipedia.org/wiki/List_of_treaties