Crosby WMD is divided into three geologic areas. Northern Burke and northeastern Divide Counties are drift plain, an area of large shallow potholes. South of this, the Altamont Moraine complex (Missouri Coteau) is approximately 15 to 30 miles wide and crosses the WMD diagonally from northwest to southeast. South and west of the Moraine lies the Coteau slope, an area of land sloping gently to the Missouri River. WPA's and easements are distributed throughout the three areas and Lake Zahl National Wildlife Refuge lies within the Coteau Slope.
Before settlement, the dominant native vegetation was mixed grass prairie. The most common native shrub was wolfberry (buckbrush) with rose and buffaloberry also being present. Groves of aspen and willow, with an occasional cottonwood, grew on the rims of wetlands.
The area was homesteaded in the late 1800's and early 1900's with farming the primary land use. Livestock production was secondary. The depression of the 1930's forced many farmers to sell land and livestock. The early 1940's, however, ushered in a period of prosperity that caused a boom in small grain production. Prairie is still being converted to cropland today.
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