Are the ozark and ouachita mountains located east or west of the mississippi river

Ozark and Ouachita mountains located west of the Mississippi river.

Located on the western side of Arkansas, the Ozark Plateau, and Ouachita mountains have distinct physiographic features. They are formed during Palaeozoic era hence they are composed of Palaeozoic sedimentary rock.  

Ozark plateau is asymmetrically shaped made of limestone, dolomite, shale dolomite, chert, etc. While Ouachita Mountains have been eroded and deformed since their formation are formed from shales, sandstones, and novaculite. Boston Mountains form a boundary between the Ouachita and Ozark mountains.

The Ouachita Mountains has a rich flora that includes the oak, pine, and hickory.