Toward the close of the last, or Wisconsin, stage of glaciation about 10,000 years ago, the ice front receded from central Iowa toward the north and, in the latitude of Browns Valley, crossed the continental divide between the Mississippi River and the drainage to Hudson Bay. After the glacier had retreated north of this divide, the meltwaters, unable to follow the natural drainage northward, were confined between the ice and the divide to the south. Thus Glacial Lake Agassiz was created. At its maximum it was 600 feet deep and larger than the combined area of the five Great Lakes today. The outlet of the lake was at Browns Valley. There the Glacial River Warren had its source and carried the overflow from the lake through the valley of the present Minnesota River. When the northern ice eventually melted away, the impounded water escaped to Hudson Bay and left behind on the floor of Lake Agassiz the lake sediments that are now the rich soils in the Red River Valley region.