Read it through once

For more than a hundred and fifty years there had been white settlements on our Atlantic coasts. These people were in intimate communication with the Indians: in the south the Spaniards were robbing, slaughtering, enslaving and converting them; higher up, the English were trading beads and blankets to them for a consideration, and throwing in civilization and whiskey, 'for lagniappe;' and in Canada the French were schooling them in a rudimentary way, missionarying among them, and drawing whole populations of them at a time to Quebec, and later to Montreal, to buy furs of them. Necessarily, then, these various clusters of whites must have heard of the great river of the far west; and indeed, they did hear of it vaguely,--so vaguely and indefinitely, that its course, proportions, and locality were hardly even guessable. The mere mysteriousness of the matter ought to have fired curiosity and compelled exploration; but this did not occur. Apparently nobody happened to want such a river, nobody needed it, nobody was curious about it; so, for a century and a half the Mississippi remained out of the market and undisturbed. When De Soto found it, he was not hunting for a river, and had no present occasion for one; consequently he did not value it or even take any particular notice of it.