▁east ▁of ▁what ▁is ▁now ▁St . ▁Louis , ▁Missouri ▁in ▁present - day ▁Southern ▁Illinois . ▁Mississ ipp ian ▁culture ▁r anged ▁from ▁the ▁Great ▁L akes ▁to ▁the ▁G ulf ▁Coast , ▁and ▁along ▁the ▁Ohio ▁River ▁and ▁into ▁both ▁the ▁low land ▁and ▁mountain ▁areas ▁of ▁the ▁S out heast . ▁ ▁Mississ ipp ian ▁settlement s ▁were ▁known ▁for ▁their ▁large ▁platform ▁earth work ▁m ounds ▁( us ually ▁trunc ated ▁py ram ids ) ▁sur mount ed ▁by ▁tem ples , ▁the ▁houses ▁of ▁war rior ▁k ings ▁and ▁pri ests , ▁and ▁the ▁bur ial ▁houses ▁of ▁the ▁el ite . ▁The ▁m ounds ▁were ▁arranged ▁around ▁large , ▁flat ▁pla zas ▁believed ▁to ▁be ▁used ▁for ▁cer emon ial ▁community ▁gather ing ▁and ▁rit ual ▁games . ▁Arch ae ological ▁research ▁has ▁shown ▁that ▁Mississ ipp ian ▁settlement s ▁such ▁as ▁C ah ok ia ▁and ▁S pi ro ▁took ▁part ▁in ▁a ▁vast ▁trad ing ▁network ▁that ▁covered ▁the ▁eastern ▁half ▁of ▁what ▁is ▁now ▁the ▁U . S . ▁and ▁parts ▁of ▁what ▁is ▁now ▁the ▁Western ▁U . S . ▁as ▁well . ▁ ▁The ▁S pi ro ▁site ▁includes ▁twelve ▁ear then ▁m ounds ▁and ▁ 1 5 0 ▁acres ▁of ▁land . ▁As ▁in ▁other ▁Mississ ipp ian - c ulture ▁towns , ▁the ▁people ▁built ▁a ▁number ▁of ▁large , ▁complex ▁earth works . ▁These ▁included ▁m ounds ▁surrounding ▁a ▁large , ▁planned ▁and ▁le ve led ▁central ▁pla za