PLATE XXXIV. 



DAKOTA COUNTY, 1888. N. H. WINCHELL. 



This county embraces great diversity of soil, surface, topography and agricul- 

 tural adaptability. It lies between the extreme eastern margin of the earlier drift 

 and the morainic deposits of the later, and therefore it was the scene of the tumult- 

 uous drainage from the ice-margin of the latter. At the same time, the outrunning 

 strike of the St. Peter sandstone, which always causes a rather sudden change of 

 about 100 feet in the average rock level, is here brought out very remarkably, and 

 cooperated with the later glacial drainage to produce a series of topographic features, 

 the full account of which must be sought in the report on this county in volume II. 

 Again, the great drainage courses of the state, the Minnesota and Mississippi valleys, 

 here unite and form the whole northern boundary. The ancient lakes, formed by 

 the damming of the Minnesota by the later glacier, shrinking in volume and shifting 

 in place from time to time as the ice receded and uncovered lower and lower outlets, 

 the changing glacial drainage courses that cross this county, including five or six 

 long terraced valleys, the gravelly delta plains formed where these debouched into 

 the equally swollen Mississippi, and the final retirement of the ice and the reduction 

 of the streams to their present size these features, and their connection with the 

 preexisting gorges of the Minnesota and the Mississippi, conspire to make Dakota 

 county one of surpassing interest to the glacialist. Similarly important glacial 

 features are spread over adjoining parts of Washington, Ramsey and Hennepin 

 counties, next north, and over the counties that adjoin the Minnesota and Cannon 

 valleys toward the south. 



The western one-third portion of Dakota county is rough with the hills of the 

 later moraine, this roughness being augmented by the older roughness of the Trenton- 

 St. Peter rock-terrace. Through this rough tract, after the Cannon valley, are found 

 in succession northward the following avenues of glacial drainage: the Chub Creek 

 valley, the Vermilion valley, with its three tributaries (one in northwestern Eureka, 

 the Prairie Lake valley and the Crystal Lake valley), of which the Crystal Lake course 

 is the principal and has a distinct connection with the Minnesota, the Mendota valley 

 passing from near Mendota through section 1, Eagan, to the northwestern part of 

 Rosemount, and its eastern fork, which lies about two miles further east, and lastly 

 the Mississippi valley, from St. Paul southward. These streams had their sources in 

 and on the ice of the later Glacial epoch, or in the glacial lakes of the Minnesota 

 valley, and they eroded and carried away a large part of the earlier drift from the 

 eastern and central portions of the county, burying its remnants more or less com- 

 pletely under the glacial debris of their own turbulent waters. 



