Which region includes fertile valley plains between sandstone ridges of the Appalachian system?

The Appalachian Ridge and Valley Region is characterized by its unique geological features, including fertile valley plains nestled between sandstone ridges. This region is part of the larger Appalachian Mountain system, where the valleys have historically provided suitable conditions for agriculture due to the rich soil. The rivers that flow through these valleys tend to promote a diverse ecosystem and facilitate farming, allowing for the cultivation of various crops.

In contrast, the East Gulf Coastal Plain is primarily characterized by flat lands and coastal features that do not align with the description of fertile valleys between ridges. The Piedmont region, while it does contain rolling hills and some valleys, does not have the same pronounced sandstone ridges as the Appalachian Ridge and Valley, and thus does not fully represent the features described in the question. The Blue Ridge region is known for its rugged mountains and high peaks, which do not incorporate the valley plains between sandstone ridges specifically described. This makes the Appalachian Ridge and Valley Region the most accurate choice reflecting these geographical characteristics.