Lake Sharpe—Big Bend Dam Archeology, History, Geology>

Big Bend Dam is located in central South Dakota 987 miles above the mouth of the Missouri River which flows into the Mississippi at St. Louis. The reservoir created by the dam is approximately 80 river-miles in length, extending upstream from the community of Fort Thompson to Pierre, South Dakota. The Big Bend Dam was the last of six major structures to be built along the main stem of the Missouri River. The reservoir (Lake Sharpe) behind the dam was raised to normal operating pool level of 1420 feet (above sea level) in late 1965 and was designed to be held at a relatively stable level year-round.

The Big Bend area takes its name from a remarkable feature of the river called the "Grand Detour" or "Great Bend" by 18th century explorers who were the first Whites to visit and describe the region. At this point in its course the Missouri makes an almost complete loop which has a length of more than twenty miles, though the shortest distance across the neck or "gorge" is little more than a mile and a half. Walking across this narrow part or following the circuitous river route, explorers and later visitors were struck by the geography of this unusual section of the valley.

Big Bend Reservoir Area, Missouri River, South Dakota. (click on image for a PDF version)

In the Big Bend area, the Missouri flowed in a trench between steep and often rugged bluffs which rose in places to several hundred feet above the channel. Established thousands of years ago, during late geologic time when the glaciers were receding, the trench marks the approximate limit of major advances of the ice sheets. As the glaciers melted and disappeared, they left deposits of "drift" or rocky soil many feet in thickness which had been transported by the ice from the northeast. This drift may readily be seen by the motorist along the bluffs east and north of the river as one approaches Pierre on Highway 34 from the southeast. West of the Missouri the present terrain results from the erosion of much more ancient formations of marine origin such as the Pierre Shale, the source of "gumbo" soils.

In the Big Bend area, only short, intermittent tributary streams empty into the Missouri from the northeast and only one larger stream, Medicine Creek, enters from the southwest. The Missouri bottom lands and the lower parts of some of the tributaries were formerly well timbered with deciduous trees such as cottonwood, willow, ash, elm, box elder, and hackberry. In certain areas along the bluffs—especially on slopes facing northeast, where suitable soil and ground water are available—groves of juniper (or cedar) add variety to the landscape.

The vast, treeless uplands above the immediate valley of the Missouri support such hardy native plants as buffalo grass and grama, which once provided pasturage for enormous herds of bison—the American "Buffalo"—a primary source of food and many other necessities of life for the Indian groups that occupied the region from early prehistoric times. Other larger animals of importance to the human occupants included elk, deer, and pronghorn antelope, with occasional bear, wolves and foxes. Smaller species such as deer, antelope and prairie dog are still to be seen. Along the timbered watercourses were numerous fur-bearers which were dependent upon the deciduous trees. With the coming of the fur traders, the barter for the pelts of these animals, and later for buffalo robes and hides, grew to major importance and strongly influenced the course of history of the Indians. Waterfowl and upland birds were also abundant, then as now, and the fly-ways of many native varieties of migratory fowl follow this part of the valley of the Missouri.

The climate of the region is one of great extremes, with hot summers and cold winters. Pierre, South Dakota, at the upper end of the reservoir, has recorded temperatures from 115° to -40°. Violent winds may spring up at any season of the year, frequently accompanied by torrential rain or heavy snow. At other times the winds raise dense dust storms. The average annual precipitation totals about 16 inches, although the actual figure varies widely from year to year; about four-fifths of the precipitation occurs in the form of summer showers.

The first human occupants of the region were chiefly dependent upon the native fauna, itself migratory, and then more abundant than at any time since. Native animals and birds provided food, clothing, materials for shelter and for many domestic and personal articles; the gathering of seeds, fruits and berries supplemented the diet.

Still larger groups made an appearance later and differed from their predecessors in practicing horticulture—the growing of foods, thus materially adding to the resources available to them. Particularly important among the new plant foods was Indian corn (or maize) because it could readily be grown by methods of primitive gardening and with proper drying could be preserved for long periods of time. Small garden plots were located on the sandy flood plains of the river, which afforded almost unfailing sub-surface moisture; essential for successful corn growing.

Through their skill in raising crops, which when dried and stored in pits or caches could be used long after the harvest, some of these communities of early horticulturalists developed a distinctive culture centered about relatively fixed villages. A reliance upon meat obtained by hunting, especially the bison, supplemented the diet of garden produce.

The remains of village sites of these semi-sedentary horticulturalists and hunters have been found in large numbers in the Big Bend area—more than 150 have been recorded. The settlements were usually located on lower river terraces just above the Missouri itself, near potable if roily water, but safely above seasonal flood levels. Despite the passage of centuries, distinctive surface contours, readily recognizable as the work of man, are still to be seen at some of the village sites. These surface indications usually are in the form of clusters of shallow circular depressions, some as large as fifty feet in diameter; in certain instances, clusters of depressions are surrounded by a shallow ditch. The circular depressions are the sites of former earth lodges and the enclosing ditch the remains of a dry moat which was usually accompanied by a palisade of upright timbers. Elsewhere, dwelling sites are to be seen scattered along the edge of terraces and bluffs and lack traces of enclosing defensive ditches.

Other less settled native peoples, who moved freely about the region following the migrating buffalo and other game, probably clung close to the Missouri and its tributaries. For both the settled villagers and the more venturesome buffalo hunting tribes and bands, the introduction of the horse—through trade with other Indian groups to the south and west—and of the gun—through trade with Whites—were of major importance since they permitted still more extensive travel over the Plains as well as more efficient hunting. Still, for these First Americans of the Northern Plains, as for the Whites who followed them, the river was the chief geographic feature of the area and the focal point of their activities.

Cultural chronology in the Big Bend Area. Sketches: Courtesy of the Missouri Basin Project, Smithsonian Institution