The human cost of the Civil War

From Team of Rivals, page 346:

The Confederates had fired the first shot. A war had begun that no one imagined would last four years and cost greater than six hundred thousand lives-more than the cumulative total of all our other wars, from the Revolution to Iraq. The devastation and sacrifice would reach into every community, into almost every family, in a nation of 31.5 million. In proportion to today's population, the number of deaths would exceed five million.