GEOLOGY OF SOUTHWESTERN IOWA. 303 



it at a point nearly fifty miles below Sionx City, between 

 which two points no other stream reaches the great river 

 on the eastern side. When the Missonri river conrsed along 

 the Iowa side of its flood-plain, however, the West Fork, 

 Little Sionx, and Maple rivers all emptied directly into it 

 as separate streams, within the same distance. Below the 

 confluence of the Little Sioux and Maple rivers the remains 

 of the ancient bed of the Missouri before referred to, are seen 

 again as a series of ponds and marshes along the base of 

 the bluffs. Similar traces are also frequently to be seen in 

 similar positions at intervals all the way to the south 

 boundary of the State, but all the streams that enter the 

 flood-plain from the uplands, southward from Maple river, 

 cross the plain and reach the great river by separate channels. 



The drainage area of the Mshnabotany river, extending as 

 it does so far to the northward, and so nearly parallel with the 

 Missouri, cuts off a considerable area that would otherwise 

 be drained directly into the last named river by smaller 

 tributaries. In consequence of this, for a distance of more 

 than thirty miles northward from the southern boundary 

 of the State, no stream crosses the flood-plain from the bluffs 

 to the great river. We see then that the numerous streams 

 which collect the waters from the western drainage slope 

 of the State, only six of them cross the flood-plain independ- 

 ently, and that these cross it within the middle fifty miles 

 of the one hundred and thirty miles of its entire length 

 in Iowa. These streams are the Keg, Mosquito, Pigeon, 

 Boyer, Soldier, and Little Sioux. 



These are the streams which bring down the greater part of 

 the tributary floods upon the great flood-plain, and if their 

 waters were controlled and passed by direct channels without 

 obstruction to the Missouri river, the complete reclaimation 

 of thousands of acres of the best lands in Iowa would be 

 thereby effected. Such a work is quite practicable, but it is 

 one of such magnitude and importance that it will require 

 combined effort for its accomplishment, and if ever accom- 

 plished, must necessarily be done upon a systematic plan. 



