That was a serious civilization.
Note to all those folks who think the Indians on the East Coast were exceptionally primitive because they left no metal implements or tools behind ~ the soils in the East are just acid enough that iron tools dropped by early English pioneers in the 1600s have totally dissolved!
We have ceramic wear produced by the Indians along the Occoquan ~ they began making European designs in the 1500s ~ but there are shards of earlier traditional Indian designs dating back hundreds of years.
“The Woodland Native Americans of 1000 B.C. to 1000 A.D. were pretty civilised.”
The mound builders (they left a site of much interest in southern Wisconsin, the name of which I cannot remember) seem to have been of a culture very different from and not ancestral to the Indians living in that region when European explorers/settlers arrived in the 1600s. My knowledge pool about these people is very shallow. Their civilization seems to have faded away without “morphing” into the culture limned in, for example, Longfellows’ Song of Hiawatha. There’s another impressive mound builder ruin near East St. Louis, Cahokia Mound, if I remember correctly, likely similar to the Pinson Community.