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The Great Oasis Culture

Archaeologists use certain words to divide prehistoric time (the time before history was recorded with words) into units. A period groups a span of years during which time the people shared similar characteristics in terms of their life styles.

For prehistoric Iowa, the four periods of human activity from earliest to most recent are the Paleoindian, Archaic, Woodland and the Late Prehistoric period—during which the Great Oasis, Nebraska (the Glenwood), Mill Creek and Oneota cultures thrived. The Paleoindian period was about 12,000 years ago. The Archaic period in Iowa was between 10,000 and 3,000 years ago. The Woodland period began about 300 B.C.E. in Iowa and lasted about 1,000 years. The late prehistoric period began about 900 C.E.

Archaeologists identify some groups of people of the Late Prehistoric period as “Great Oasis.” The Great Oasis culture is thought to have evolved from a Woodland culture by 900 C.E. The Great Oasis groups lived in western and central Iowa. Great Oasis culture groups can also be found in southwestern Minnesota, eastern Nebraska and South Dakota. Archaeologists believe that later cultures like the Mill Creek developed from the Great Oasis.

Great Oasis Villages

Great Oasis people usually built their villages on terraces above the floodplain of a nearby river or stream. A number of these sites in Iowa have been excavated. These excavations tell archaeologists something about the type of houses and floor plans used by the Great Oasis people. Houses were long rectangles. They were built into a shallow pit about one and a half feet deep. House walls had vertical posts. Sticks were woven between the posts and covered with mud. This is called "wattle and daub" construction. A covered entrance came out from the narrow end of the house. The roof may have been grass thatching.

Each house had a central fireplace and many cache pits. Cache pits were holes used to store food and other items. Once their original contents had spoiled or were disturbed by rodents, these pits were filled with earth and garbage. When archaeologists excavate the pits, they find broken pottery, stone and bone tools, chipped stone flakes, and animal and plant remains. By studying these remains, it is possible to discover what time of year the houses were lived in and what the Great Oasis people ate.

Hunters and Growers

The Great Oasis people may have lived in villages only during certain times of the year. They may have left for group bison hunts. Or they may have split into smaller groups to set up garden plots at other locations. Unearthed cache pits have revealed the remains of deer, elk, bison, wolf, coyote, rabbit, gopher, mouse, mole, frog, turtle, snake, birds and fish. Many deer and elk bone have been uncovered. This makes archaeologists think that these were the two most important animals the Great Oasis people hunted. Deer and elk may have been more important than bison.

Seeds of com, sunflower, and squash or gourd show that the people tended gardens. The remains of goosefoot, pigweed, smartweed, hackberry and walnut have been found. It suggests the Great Oasis people collected these wild plants.

Various animal remains suggest that the site was lived in throughout the fall, winter and spring months. The seasonal growth rings on fish scales pointed to fall occupation. A deer skull with shedded antlers suggested residence during the winter. A bird's medullary bone, which appears only during the reproductive period, was evidence that the site had been lived in during the spring.


The Great Oasis people used stone tools that are much like those used by other Plains cultures. Many small, triangular, side-notched points have been found. This might be a clue that the bow and arrow had replaced the spear and dart used by earlier groups. Many of the chipped stone tools are made of stones that must have been traded from other tribes. Quartzite and flint from the Dakotas and sandstone from Wisconsin have all been found in Great Oasis sites in Iowa.

Ceramic artifacts tell more about the Great Oasis people. These are globe-shaped jars with rounded bases. These jars show marks that suggest that the Great Oasis pounded the jars into shape with a cord-wrapped paddle. The cord marks were usually smoothed over before decoration was applied. This process of smoothing over the cord marking is a typical Woodland trait. The most common ceramic type, Great Oasis High Rim, has a thin, straight, parallel-sided rim that usually has a flattened lip. The rim was decorated with cut lines. A ceramic type that was common at Des Moines River Valley sites had a low, wedge-shaped lip decorated with tool marks. A third type has also been identified. It has an S-shaped rim.


It appears that Great Oasis people practiced several different burial customs. Sometimes human bone is found in village burials or refuse areas. Most Great Oasis cemeteries appear to be on hills or bluff tops away from the living area. Both single and multiple burials have been found and include both bodies and the remains of cremation. Sometimes the burials are in mounds.

There are remains from two big Great Oasis cemeteries. One is in the city of Des Moines and another is south of Redfield in Dallas County. At each site, close to 100 individuals were found. Many of the bodies had their knees drawn up to their chest, and had a variety of grave items with them. The grave items included whole pots and hundreds of small snail shell beads. The snails lived in streams and rivers of the eastern United States. Cross-shaped artifacts made from clamshell were also found at the West Des Moines cemetery, but have not been found at any other Great Oasis sites.


The relationship between Great Oasis people and other groups of the same period is not known. There is evidence that trade was established over long distances. It is not known what products Great Oasis people traded. The snail shell beads show that they had contacts to the south and east. Some archaeologists believe the Iowa groups may have traded meat or skins for these items. These items are highly perishable. They rarely last long enough to be found by later archeologists.

Adapted from an article by Lynn Alex in Office of the State Archaeologist Educational Series Pamphlets, 2002.



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