For information concerning all the countries of the West which have not yet been visited by Europeans, consult the account of two expeditions undertaken at the expense of Congress by Major Long. This traveler particularly mentions, on the subject of the great American desert, that a line may be drawn nearly parallel to the 20th degree of longitude (meridian of Washington),1 beginning from the Red River and ending at the River Platte. From this imaginary line to the Rocky Mountains, which bound the valley of the Mississippi on the west, lie immense plains, which are generally covered with sand incapable of cultivation, or scattered over with masses of granite. In summer these plains are destitute of water, and nothing is to be seen on them but herds of buffaloes and wild horses. Some tribes of Indians are also found there, but in no great numbers. Major Long was told that in traveling northwards from the River Platte you find the same desert lying constantly on the left; but he was unable to ascertain the truth of this report. (Long's Expedition, Vol. II, p. 361.)
However worthy of confidence may be the narrative of Major Long, it must be remembered that he passed through only the country of which he speaks, without deviating widely from the line which he had traced out for his journey.