The whole nation was in the classroom of war. The imperious call for leaders of every grade and in all ranks of activity developed everywhere out of raw material captains of men, engineers, organizers, business directors, financiers, inventors, directors of activities, on a scale before undreamed of in America. It was a college course in which were developed efficiency and self-reliance and wideness of vision and courage and restless activity, and it produced a most remarkable generation of men. The armies in the field and those other armies that handled the railroads and the mills and the finances and supplies, were sons all of them of a race that had been doubly picked in the generations before, for only the bravest and most virile in body and soul had dared to break from their old-world surroundings and plunge into the untracked West, and only the fittest of these had survived the rigors of pioneer days. And the war schooled this remnant and widened their vision and ground out of them the provincialism that had held them so long to narrow horizons. It was not until 1865 that Emerson could write, "We shall not again disparage America now we have seen what men it will bear." But the chief difference between these men and the early men that had so filled him with apprehension in the thirties and the forties, was in the schooling which had come from the five years of tension when the very life of the nation was in danger. The disbanding of the armies was followed by a period of restlessness such as America had never before known. The whole population was restless. "War," says Emerson, "passes the power of all chemical solvents, breaking up the old adhesions and allowing the atoms of society to take a new order." The war had set in motion mighty forces that did not stop when peace was declared. Men who had been trained by the war for the organizing and directing of vast activities turned quickly to new fields of effort. The railroads, which had been vastly enlarged and enriched by the war, pushed everywhere now with marvelous rapidity; great industries, like the new oil industry, sprang into wealth and power. The West, lying vast and unbroken almost from the farther bank of the Mississippi, burst into eager life, and the tide of migration which even before the war had turned strongly toward this empire of the plains quickly became a flood. Railroads were pushed along the wild trails and over the Rocky Mountains. The first transcontinental road was completed in 1868. The great buffalo herds were exterminated in the late sixties and early seventies; millions of acres of rich land were preëmpted and turned over to agriculture; the greatest wheat and corn belts the world has ever known were brought into production almost in a moment; bridges were flung over rivers and cañons; vast cities of the plain arose as by magic. Everywhere a new thrill was in the air. The Civil War had shaken America into eager, restless life.