The Mill Creek 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.

A thousand years ago farming villages were set up along the Missouri River and its tributaries in northwestern Iowa, South Dakota, and southern North Dakota. Archaeologists call these sites the “Middle Missouri tradition.” The Iowa sites of this tradition make up the “Mill Creek culture.”

Most archaeologists believe that Mill Creek developed from the Great Oasis culture. The Great Oasis culture existed in Iowa around 900 C.E. The Mill Creek culture was also influenced by other cultures in Iowa and neighboring states. Mill Creek sites occur near the Big Sioux and Little Sioux rivers and their tributaries: Broken Kettle Creek, Mill Creek, Brooke Creek and Waterman Creek.


Mill Creek sites are often large mounds, sometimes 10 -12 feet high, which cover as much an acre. These mounds were formed from the people constantly building over their filled-in trash heaps and the ruins of older houses. In some cases, the remains of three houses have been found on top of one another. Each house was built in a shallow pit and had an extended entry at one end. Vertical timber posts had small branches woven between them (wattle). These branches were plastered with grass mixed with mud (daub) to form the walls. Archaeologists are not sure of the layout of the timber posts supporting the roof. It may have had two rows of posts running along the length of the house on either side of the fireplace.

Cache pits were dug both inside and outside of houses. These pits were used to store extra food and other items. Archaeologists know from historical accounts that rodents would sometimes disturb these pits. Sometimes the contents would rot. If this happened, the left-over contents were removed and large, empty pits remained. Since it was dangerous to have a large open pit, the holes were filled with rubbish—broken pottery, tools, and garbage—and then covered. These are the artifacts archaeologists find in the pits when they are excavated.

Artifacts Reveal History

A large number of bone tools, pottery and burned plant remains have been found at Mill Creek sites. These suggest that these people were successful farmers who tended gardens of com, beans, squash, pumpkin and sunflower. Since the prairie grasses of the Midwest had a tough, thick root system, the sod was almost impossible to cut through. So the natives generally farmed the loose, rich, river bottomland.

They used bone hoes and bone or wooden digging sticks. Hoes are a common item in Mill Creek sites. Most were made from bison shoulder blades (scapula). The scapula was also used to make a blunt-ended knife. The knife had a straight edge on one side and a convex-concave edge on the other. This knife was probably used in cutting items such as squash.

One site along Waterman Creek shows evidence of a ridged field or raised garden bed on a terrace above the creek. Ridged fields may have been a back-up to bottomland gardening. If the bottomland gardens flooded, crops could still be tended in the ridged fields.

Archaeologists think many of the animal bones uncovered at the Mill Creek sites come from the food the people ate. Small game, fish and birds were hunted all year. Animals were killed with bow and arrows that had small, side-notched projectile points.

According to the evidence at some sites, Mill Creek people probably left their village at certain times to hunt larger animals. Once crops were planted, most of the people could join in a bison hunt. Some members would probably stay home to take care of the crops, the aged, and the very young children. A second bison hunt may have taken place in the fall.

Animal Parts Provide Many Uses

From the presence of certain bones found in the village sites and the absence of others, it is likely that butchering occurred at the kill site. Parts of the animal were cut up or eaten immediately after the kill. The bones were left at the kill site. Other chunks of meat, and the attached bones, were brought back to the village to be dried and stored.

The bones of mammals, fish and birds were made into many items. The bone of bison, elk and deer were used to make hide grainers (a tool for scraping and smoothing the inner surfaces of hides), shaft straighteners (a bone drilled with holes and use in straightening and remove bumps in arrow shafts), hoes, knives, sickles and flaking tools (used for carving rock). Mill Creek peoples caught large catfish using bone fishhooks. Bone needles and pointed awls were made of bison bone, bird bone or the spine of drum fish. These needles let Mill Creek people sew skins and work basket fibers. Porcupine quills flattened with spoon-like pieces of bone were probably used for decorations.

Decorations were also made from snail shell and conch shell beads, shell pendants, carved bone pins, and teeth from bear, dog and beaver. These decorations came from the hunted animals and through trade. In some cases, the bones used by Mill Creek people in Iowa come from animals that can no longer be found in the area. The passenger pigeon is now extinct. And the river redhorse (a type of sucker fish) can no longer be found in the state.

The skins and feathers of animals were used on ceremonial items. Historic Plains groups, such as the Osage, Omaha, and Arikara, had medicine bundles made of bird skin wrappings filled with sacred objects. Stuffed bird skins also served as personal “good luck charms.” In order to give some form to the bundle, the skull and bones of the wing and feet would be left attached to the skin. Archaeologists are not certain these bird bundles existed in prehistoric times. However, many bird bones from the feet, wing, and skull found together have been uncovered. This evidence strongly suggests they did.

At the Brewster and Phipps sites in Cherokee County, there were many lower wing and foot bones of hawks, eagles and falcons. This suggests that Mill Creek people were hunting or trapping these birds. Maybe the claws, wings and tail fans were used in decorative and ceremonial objects such as headdresses.


Mill Creek potters made a wide variety of containers including bowls, flat-bottom rectangular pans, seed jars, wide-necked bottles, hooded water bottles, jars, and ollas (wide-mouthed water jars). Most of the pottery was made from crushed granite or sand temper. Temper was used to keep the clay from cracking when it was heated. Ground clamshell has been found in a few pieces. The surface of the pot almost always was smooth.

The pots were decorated on the lip, rim or shoulder area. Patterns like triangles and diamonds were cut into the clay. Running deer and weeping eye are the names given to two types of patterns. Some pots were colored by black paint or red slipping (where a liquid mixture of water and colored clay is applied to the pot before firing). Some of the pots have loop handles or handles looking like small animals or birds.

The following items were found at Mill Creek sites and in and around Cahokia, Illinois:

  • Earspools (pulley-shaped stone or bone earrings)
  • Chunky stones (disc-shaped stones probably used in athletic games)
  • Shell pendants
  • Scalloped-edge shell gorgets (armor for the throat area)
  • Certain snail shell beads from the southern U.S.
  • Marine (counch) shell traded from the Gulf of Mexico

The Hartley Fort site in the northeast corner of Iowa contained both Mill Creek and Mississippian pottery. Archaeologists believe this site was a point of contact between the Mill Creek of northwest Iowa and the natives of Cahokia, Illinois.


While Mill Creek people may have traded peacefully with other groups, there is reason to believe that not all of their contacts were friendly. Mill Creek sites in O'Brien County had ditches on at least three sides. The fourth side faced the nearby stream so that these sites were protected all around. At Wittrock a log stockade (wall of posts with pointed tops) had been built on the interior side of the ditch. There may have been log walls at other sites as well. At Double Ditch two parallel ditches were dug.

Mill Creek People Disappear

One possible reason for the disappearance of Mill Creek culture from Iowa was pressure from hostile groups. Exactly who these hostile groups might have been is unknown. Mill Creek villages may have been rivals with one another. Some climatologists suggest that about 1200-1250 C.E., the climate became drier making it harder to farm. In addition, the people had probably used up most of the nearby timber for fuel and house construction. Faced with these conditions, Mill Creek people seem to have abandoned their villages. Before the end of the 13th century, they had moved away from Iowa.

It has been suggested that Mill Creek people gradually migrated up the Missouri River. They might have become a part of the later Middle Missouri tradition sites of the Dakotas. Archaeologists believe that the Sioux-speaking Mandan and Hidatsa developed from these later groups. These people were living in large, permanent, earth lodge villages at the time of contact by European explorers.


  • Duane C. Anderson, “The Mill Creek Culture,” The Goldfinch 5, no. 3 (February 1984): 2.


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