Most North Dakotans know that the Red River Valley is a portion of the former lakebed of glacial Lake Agassiz, but there are other glacial lake plains in the state that are less well known.
Glacial Lake Agassiz formed during the end of the last ice age as the glacier retreated. The lake's area is now known for its flat topography and agricultural productivity, which is largely due to the lake deposits that formed deep rich soils that make for very productive farmland. And unlike many other areas of eastern North Dakota, one does not see many rock piles in these fields.
Among the less well-known glacial lake plains is glacial Lake Souris. Like glacial Lake Agassiz, this lake also formed at the end of the last ice age. It covered a portion of southwest Manitoba and southeast Saskatchewan, and in North Dakota a strip of land between Turtle Mountain and the Souris River southward to near Denbigh and eastward to the Rugby area. As such, it covered much of Bottineau and McHenry counties as well as portions of Rolette and Pierce counties.
Like glacial Lake Agassiz, glacial Lake Souris is also is quite flat, contains deep rich soils, and is some of the most productive farmland in the state. There are also areas of near-shore and off-shore sandy areas and sand dunes associated with the lake, particularly around Towner, Bantry, and Denbigh.
There are a few other glacial lake beds in eastern North Dakota. Glacial Lake Cando in the Cando area occupies parts of Benson, Ramsey, and Towner counties, while glacial Lake Minnewaukan is an earlier version of the present-day Devils Lake. And in Dickey and Sargent counties, to the north and south of highway 11 between Forman and Oaks and the James River is glacial Lake Dakota which continues southward into South Dakota’s James River basin.
So, as you travel these or other expansive areas of relatively flat landscapes with rich soils and few (if any) rock piles in the fields, keep in mind that they may also be glacial lake plains. They are often important agriculturally productive areas.
