Scientists, environmentalists, and anyone who lives within a hundred miles of the winding Mississippi River will tell you—have told you, repeatedly, for 150 years—that efforts to tame the river have only made it more feral. But scientists would like more than intuition, more than a history of 18th-century river level gauges and discharge stations, more than written and folkloric memory. They would like proof. Luckily, rivers inscribe their history onto the landscape.