Le Page du Pratz, The History of Louisiana, Or of the Western Parts of Virginia and Carolina
“ III. The Upper Louisiana we call that part of the continent, which lies to the northward of the mountains above mentioned in latitude 35°. This country is in many places hilly and mountainous for which reason we cannot expect it to be so fertile as the plains below it. But those hills on the west side of the Missisippi are generally suspected to contain mines, as well as the mountains of New Mexico, of which they are a continuation. ”
