The Mississippi Alluvial Plain covers the eastern third of Arkansas. Rising amidst this flat landscape of cropfields and wetlands is Crowley's Ridge, a 200 mile chain of forested hills, stretching from southeast Missouri to Helena, Arkansas. This ridge is an erosional remnant from the Pleistocene, a peninsula between the Mississippi River, that flowed to its west, and lower Ohio River, that flowed to its east. Late in the Pleistocene, the Mississippi eroded through its east bank near Cairo, Illinois, joining the Ohio and abandoning its original, western channel.
The bedrock of Crowley's Ridge is composed of late Paleozoic (Cretaceous) and early Tertiary sediments; during the Pleistocene, a thick layer of loess (wind blown glacial dust) was deposited atop the ridge, enriching the soil and setting the stage for its unique flora. Though close to the Ozarks of Missouri and Arkansas, the forests of Crowley's Ridge are more typical of the southern Appalachians, harboring a mix of oak, beech and yellow poplar.
Up to 15 miles wide and with an elevation ranging from 250 to 400 feet, this forested ridge was a magnet for early white settlers in the region, a welcome alternative to the flat wetlands on either side. Named for Benjamin Crowley, who established a homestead on the ridge in the early 1800s, this higher, drier strip of land is now dotted with eastern Arkansas' larger cities (Paragould, Jonesboro, Helena and others); a Scenic Parkway runs atop the ridge, connecting these cities.
