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Interior River Valleys and Hills

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NameColor on MapEPA Code‡
Wabash-Ohio Bottomlands72a
Glaciated Wabash Lowlands72b
Green River-Southern Wabash Lowlands72c
Upper Mississippi Alluvial Plain72d
Middle Mississippi Alluvial Plain72e
River Hills72f
Southern Ozarkian River Bluffs72g
Caseyville Hills72h
Western Dissected Illinoian Till Plain72i
Southern Illinoian Till Plain72j
Cretaceous Hills72k
Karstic Northern Ozarkian River Bluffs72l
Wabash River Bluffs and Low Hills72m

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.


Partially Complete
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Complete w/ Images

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About the Interior River Valleys and Hills

The Interior River Valleys and Hills, referred to in some documents as the Interior River Lowland is a region of flat bottomlands and surrounding hills along the Mississippi, Missouri, Illinois, Ohio, and Wabash rivers, where these smaller rivers all flow together into the Mississippi. The region includes a narrow strip of eastern Iowa, a large region of western and southern Illinois, a portion of eastern Missouri, a small portion of southwestern Indiana, and a small region of western Kentucky.

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