"The map is truly a beautiful bit of geologic history. For more info on it, see my previous blog post. So many amazing swirls and details in the river's course. Rendering it as a slippy map makes it easy to see the map in great detail, for instance the Old River Control Structure, a site threatened by the floodwaters of 2011. (Interestingly, the modern channel was built on relatively dry land.) The opacity slider (or text box) in the upper right lets you look through the Fisk map to a contemporary Google map. Check out this flood plain, for example. The satellite view contains echoes of the various old meanders, too, like these curved fields."