This study examines high-terrace chert-gravel deposits preserved in several locations near and north of Toledo at the eastern edge of the Flint Hills in Chase County, Kansas. High-terrace gravel deposits are situated in ascending steps north of the Cottonwood River valley at three levels from approximately 90 to 150 feet (×28-45 m) above the Cottonwood River channel. All deposits contain exotic quartzite pebbles and represent the Old Osage River, which gradually shifted southward as it eroded into the modern valley. Assuming a late Pliocene age for the highest terrace gives a vertical incision rate of 1.5 cm/1000 years and a lateral migration rate of 2.2 m/1000 years. The Toledo vicinity provides confirmation for the asymmetric history of valley incision presumably due to regional crustal tilting downward to the south.