When it comes to climate-change-inspired threats, it is rising sea levels we hear most about. But if the oceans are, as Herman Melville put it, "the tide-beating heart of the earth," rivers are its circulatory system. In the United States, there is no river more storied, symbolic, and vital than the Mississippi, and none, to use Mark Twain's word, more lawless. The struggle to control it has been going on nearly as long as there has been human civilization on its banks, and the attendant drama and dangers have been memorialized by many writers, among them Twain and, in his seminal 1987 New Yorker account, John McPhee. Now Simon Winchester, the consummate, critically acclaimed storyteller and bestselling author of Atlantic and The Professor and the Madman, turns his eye to what could well be the height of the battle, one increasingly doomed by man's interference. The most fateful instance of this interference was accomplished by an inventor and steamboat captain, Henry Miller Shreve, in the nineteenth century. In vivid detail, Winchester re-creates the smashing and digging and the great man- and steam power that Shreve wielded to clear the river of snags and logjams and, in order to shorten the passage to New Orleans, carve an entirely new channel for it. What no one foresaw was that his celebrated shortcut, Shreve's Cut, would form a sloping chute to an adjacent river, the Atchafalaya, and, aided by gravity and shifting weather patterns, increasingly tempt the waters of the Mississippi in its direction. Resisting this trend with ever more ingenious methods (and ever more expense) began just after, first with a system of levees, then with added spillways, and, finally, with the conception and construction of a floodgate system, the Old River Control Structure, still in place today. And the stakes are high: If--many say when--the Atchafalaya captures the Mississippi's stream, it will be the end of life as it's currently known in the American South. The great cities of Louisiana--New Orleans and Baton Rouge--would be rendered fetid swamps; entire sections of the American infrastructure, from pipelines to electricity and water supply, would collapse. Homes would be displaced and livelihoods, if not lives, would be lost. Deftly combining the hydrological and the historical, Winchester tours the challenges that upped the ante on the Mississippi River Commission's duty to protect the watershed and its inhabitants: the upheavals that came in the form of the Great Flood of 1927, one of the most destructive natural disasters of all time, displacing more people than almost any event in American history, and the record-breaking inundations of 1937 and 1973. He pays tribute to the Army Corps of Engineers, for their Herculean efforts to keep the river on its current track, and to one civilian, Albert Einstein's son Hans Albert Einstein, a hydraulic engineer and one of the main architects of the mighty control structure that continues to divide the Mississippi from the Atchafalaya. But how long can it hold in a time when extremes of weather are the norm, when storms come faster and more furiously, sending sediment-loaded water pounding against the floodgates--events that not only pit man against nature but, given that we cannot always agree which causes and correctives to pursue, man against man? In this elegant synthesis of past and present, the exigencies of the natural world and the human, Winchester offers an engrossing cautionary tale that readers cannot afford to ignore. It is a call to arms that asks whether accepting defeat--letting nature take its course--may be the only way to win.