Cedar Creek Canyon, also called simply Cedar Canyon, is a topographical feature located in Allen County, Indiana. It is a very straight, narrow gorge about 50 to 100 feet (15 to 30 m) deep that contains part of the lower segment of Cedar Creek, the largest tributary of the St. Joseph River. The canyon originated at the end of the last ice age as a tunnel valley, a channel under the Erie Lobe of the Wisconsin Glacier that discharged meltwalter under considerable pressure into the ancestral Eel River, a tributary of the Wabash River. Cutting through the north limb of the Wabash Moraine, a debris deposit left by the retreating ice, the discharge left a large outwash fan that blocked the Eel, diverting its upper portion into the canyon in a classic example of stream piracy that formed today's Cedar Creek. This was part of a general drainage reversal that occurred in northeastern Indiana as the Maumee River opened and captured drainage that was previously part of the watershed of the Wabash.