Cedar Bluffs is a 223-acre preserve featuring a scenic forested bluffland with sandstone cliffs. It is located ten miles west of Oskaloosa in southwestern Mahaska County. The interesting flora of Cedar Bluffs caught the attention of botanists as early as 1919. It was acquired in 1990 by the Mahaska County Conservation Board with assistance from the Iowa Natural Heritage Foundation, and was dedicated in 1997 as a biological, geological, and archaeological state preserve.
The preserve is immediately upstream of the confluence of Cedar Creek with the Des Moines River, within the Southern Iowa Drift Plain landform region. The scenic terrain includes 100-foot bluffs of sandstone, box canyons, and small waterfalls. The colorful reddish sandstone outcrops provide one of the best exposures of Cherokee Group sandstones known in southern Iowa. These “channel sandstones” were deposited in ancient river channels that flowed westward across Iowa during the Pennsylvanian period of geologic time, about 300 million years ago. Closer inspection of the rocks reveals intricate cross-bedding, as well as erosional contacts, ripple marks, basal conglomerates, and coalified fossils of plant stems, twigs, leaves, and trees. The sandstone cliffs exhibit huge vertical fractures that have separated large blocks of sandstone from the bluffs in some places. Collapse and breakup of sandstone masses from these fractures have generated large-block talus fields on the lower slopes. Views from the bluff top offer a spectacular vista of the river valley.