The Transition Hills and Valleys Ecoregion are often referred to, in part, as an extension of the Appalachian Mountains Interior Plateau ecoregion into the Coastal Plains Region and lies between the lower Coastal Plains Region to the west and south and the higher elevation Appalachian Mountains Region to the east and north.

However, in actuality, this ecoregion is only a transition area between the two regions known as the Southeastern Plains Ecoregion (12M) and Interior Plateau Ecoregion (10N).

The Transition Hills are a small ecoregion which is located in southeastern Tennessee near the conjunction of the Mississippi-Alabama state border. This ecoregion extends southward into both Mississippi and Alabama along both sides of this state line. This ecoregion includes areas of northeastern Mississippi and northwestern Alabama as well as a larger area across central Alabama.

With characteristics of both the Southeastern Plains and the Interior Plateau ecoregions, this ecoregion consists of open hills with broad, round tops and steep sided slopes. The area is underlain by top layers of Cretaceous-age deposits of silt, sand, clay, and gravel that originated as coastal plain sediments, under which are older layers of limestone, shale, and chert.

Streams here tend to have low to moderate gradients. Especially towards the south of this region, and most waterways have cut through the easily eroded coastal plain sediments to reach the lower, older layers of the Mississippian, Devonian, and Silurian-age rocks. As such, soil types here are diverse and vary significantly between those area that are hills (uplands) and those which are the valleys (bottom lands).

Originally, these hills and valleys were covered with oak, hickory and pine forest with the dominant trees including: white oak (Quercus alba), southern red oak (Quercus falcata), black oak (Quercus velutina), post oak (Quercus stellata), Chestnut oak (Quercus montana), American sweetgum (Liquidambar styraciflua), various hickories (Carya sp.), shortleaf pine (Pinus echinata), and some Virginia pine (Pinus virginiana).

Both the chestnut oak and the Virginia pine attain their south westernmost range limits here, even though there are a few scattered chestnut oak populations slightly farther west.

Although this region is primarily forested with the oak, hickory and pine forests, there are small areas of cropland and pasture land in the narrow valley bottoms and on gently sloping ridges.

Natchez Trace Trail

Natchez Trace Parkway