When the glacier dam retreated to this point, where today Slippery Rock Creek enters the Slippery Rock Gorge at Kennedy Mill, it opened a pass and Lake Edmund drained completely between the glacier on the right (west) and the hill on the left (east). This extended the gorge to the north from Muddy Creek to Kennedy Mill, and completed the diversion of Slippery Rock Creek from a west-flowing stream to the present south-flowing stream. Prior to glaciation, this location was the mouth of north-flowing McConnells Run where it entered the west-flowing Slippery Rock Creek.
Upstream from this point, Slippery Rock Creek flows in a wide valley formerly occupied by glacial Lake Edmund. From here to its confluence with Connoquenessing Creek, it flows within the gorge. The gorge has changed little since glacial lake drainage past here ended, about 23,000 years ago.
Slippery Rock Creek is flowing over the old mill dam, used by Kennedy Mill from about the late 1860s to the 1920s. The mill was torn down in 1933.