To farm their crops of corn, squash or pumpkin, people living along the Big and Little Sioux rivers in Northwest Iowa used hoes made from the shoulder blades of elk, bison or deer.

They fashioned arrows from bones to hunt small animals and made hooks to catch fish. The artisans crafted and decorated pottery jars. They sharpened bones or stones into awls to weave baskets, work hides and sew clothes.

They scraped out hard dirt floors for their lodges, which had roofs and walls constructed out of timber and a mud plaster. They traded with other groups from hundreds of miles away. Someone living north of Stone State Park lost a necklace made out of small snail shells that came from the Ohio or southern Mississippi rivers.

Who were these people?

They are described by archaeologists as the Mill Creek Culture. They lived along the Big Sioux and Little Sioux rivers and their tributaries in Woodbury, Plymouth, Cherokee, O'Brien and Buena Vista counties. When they lived is what makes this story interesting.

They called this area home in the 12th century -- from 1100 to 1200 A.D. Then they disappeared. And, no one quite knows why, Lynn Marie Alex, director of education and outreach for the Iowa Office of Archaeology, told me.

The state office at the University of Iowa in Iowa City has been the repository of thousands of Mill Creek artifacts -- many coming from the Kimball and Broken Kettle sites in southern Plymouth County. The Kimball site is just north of Stone Park between the Big Sioux River and the Loess Hills.

"In the 1920s and 1930s, people dug up the Kimball site and most of the artifacts were sent to the state," Steve Hansen, director of the Sioux City Public Museum, said.

When the new museum opens in November 2010, the state will return many of those artifacts to be placed on permanent display. He saw many of the items earlier this year.

"It's like being in a candy store from a museum standpoint," he gushed. "We're in the process of making those selections on what we want back here to tell the story of the Mill Creek Culture."

Alex added, "Many of the stone and bone items are in fine condition. ...One of the things that is so beautiful is the bone artifacts we found made from large mammals. Sometimes they used bird bones for everything from gardening tools to hoes to the beautiful little fish hooks. Some of the awls have very sharp points and you kind of wonder if they just weren't lost."

None of the artifacts must be returned to Indian tribes.

"We did some recent work at the Kimball site this year. We took geophysical equipment like ground penetrating radar and magnetic surveys that allows you to discover things that lie beneath the ground."

The survey was conducted as part of a larger project involving searching for ancient artifacts in the Loess Hills. The surveys revealed at least 20 house floors underground at Kimball. One of the core samples retrieved what was left of that string of snail beads. At any given time, she estimated 100 to 150 people called that village home.

The Mill Creek people probably moved north to South Dakota. They might have abandoned their villages due to changing climate conditions, the loss of timber and/or the arrival of the Oneota people.

Many archaeologists believe the Mill Creek people evolved into the Mandan and Hidatsa tribes.

While there is a lot still to be excavated at the Kimball site, Alex said there are no plans to do so.

"We are nominating that site to be on the National Register of Historic Places," she said. "That site is on land protected by the landowner and not in imminent danger."

The Broken Kettle site also is in private ownership.

"We are excited about the new museum where these items can be showcased," she said.