The most extensive tract of valley country east of the Mississippi is that situated within the bluffs of this river, usually denominated the American Bottom, extending from the mouth of the Ocoa, or Kaskaskias river, northwardly to that of the Missouri. This spacious bottom, although at present elevated much above the range of the highest freshets, is nevertheless alluvial. Its length along the Mississippi is about eighty, and its average breadth about four miles. It is generally destitute of a timber growth, except along the margin of the river, upon which there is a skirt of woodland extending almost from one end of the tract to the other. The alluvion of the American Bottom is composed of the rich mud brought down by the turbid Missouri, united with an abundance of vegetable matter yielded by the waters of the upper Mississippi, which also characterizes the bottoms of this extensive river from the Missouri downward to its mouth. Upon this bottom are situated the town of Kaskaskias, the villages of Prairie de Rocher, Harrison, Prairie de Pont, Cahokia and Illinois, together with many other settlements. On the same side of the river another large tract of valley land, called the Mississippi Bottom, commences a few miles below the mouth of the river Kaskaskias, and extends downwards along the Mississippi, between fifty and sixty miles, having an average width of about three miles. This tract, in regard {207} to soil and aspect, is of a character similar to that of the American Bottom, except that the former is more plentifully stocked with timber. Besides these, there are numerous other bottoms on the Mississippi, within the limits prescribed for this report, all of which are composed of a rich alluvion. Those in particular situated below the confluence of the Mississippi and Missouri are possessed of a soil exceedingly luxuriant, being composed, as before observed, of the rich and fertilizing mud deposited from the water of the Missouri. Most of them are covered with deep and heavy forests of timber, accompanied with a luxuriant undergrowth of vines, shrubs, grass and other herbage. The bottoms of the Wabash, Kaskaskias, Illinois, and Rock rivers, are also made up of a rich alluvion of sand and loam, containing a large proportion of vegetable mould. Their surfaces, like those of the Mississippi bottoms, are generally flat, exhibiting tabular elevations or benches, formed by the washing of their rivers at different periods. Large tracts of prairie land are to be met with upon them; but for the most part the proportion of woodland is amply sufficient to supply the adjacent country with timber and fuel.