The coolest part of the park we have seen so far are the grindstones. These are rounded rocks found in potholes in the river that formed in the post-glacial river. The following series of graphics tell the story.
Then rocks get caught in the potholes and swivel with the currents. Over time, the rock is ground round.
Here are some more shots of the St. Croix river.
Gerald and Bruce.
The damn located upriver from the campground.
You can see how the boulders have been worn smooth along side of the river.
There are towering cliffs everywhere in the park.
The leftover remains of an earlier stage of a dragonfly's existence.
Along the river is this brass plaque.