The height of our mountains has not yet been estimated with any degree of exactness. The Alleghaney being the great ridge which divides the waters of the Atlantic from those of the Missisipi, its summit is doubtless more elevated above the ocean than that of any other mountain. But its relative height, compared with the base on which it stands, is not so great as that of some others, the country rising behind the successive ridges like the steps of stairs. The mountains of the Blue ridge, and of these the Peaks of Otter, are thought to be of a greater height, measured from their base, than any others in our country, and perhaps in North America
this is pre L&C of course but i'm not sure how he wouldn't have got word of at least the sierra from the spanish somehow. or the volcanos of mexico.