The Johnstown Flood by David McCullough Page A

clay. They were laid up one on top of the other after each layer had been packed down, or “puddled,” by allowing it to sit under a skim of water for a period of time, so as to be watertight. It was a slow process. And as the earth wall grew increasingly higher, it was coated, or riprapped, on its outer face with loose rocks, some so huge that it took three teams of horses to move them in place. On the inner face, which had a gentler slope, the same thing was done, only with smaller stones.
    The spillway, as Welsh had stipulated, was not cut through the dam itself, but through the rock of the hillside to which the eastern end of the dam was “anchored.” The spillway was about 72 feet wide. The over-all length of the breast was just over 930 feet. The width on top was about 20 feet. The thickness at the base was some 270 feet.
    At about the exact center of the base, there were five cast-iron pipes, each two feet in diameter, set in a stone culvert. They were to release the water down to South Fork, where it would flow on to the Johnstown basin by way of the Little Conemaugh. The pipes were controlled from a wooden tower nearby. On June 10, 1852, the work on the dam was at last completed; the sluice pipes were closed and the lake began to fill in. By the end of August the water was 40 feet deep.
    But about the time the dam was being finished, J. Edgar Thomson, who was then chief engineer for the up-and-coming Pennsylvania Railroad, was making rapid progress with his daring rail route over the mountains, which included what was to become famous as the Horseshoe Curve. The canal was about to be put out of business.
    The Pennsylvania was racing to complete a route west to compete with the New York Central, the Erie, and the B & O, which were each pushing in the same direction. The last part of the run, from Johnstown to Pittsburgh, was ready in late 1852. On December 10, six months after the South Fork dam had been finished, a steam engine made an all-rail run from Philadelphia to Pittsburgh. J. Edgar Thomson became president of the road about the same time, and the company was on its way to becoming within a very few years the biggest and far and above the most powerful single force in the state (and in the Statehouse); the biggest customer for nearly everything, but especially coal, iron, and steel; the biggest employer; and the biggest influence on the way people lived from one end of Pennsylvania to the other. By the end of the ’80’s it would be the mightiest of the nation’s many mighty railroads.
    The effect of the new railroad on the state’s troublesome, costly, and beloved canal system was disastrous—almost immediately. Within two years after the railroad opened, the legislature voted to put the “Main Line” up for sale for not less than $10 million. Understandably there were no takers. The one likely prospect was the Pennsylvania itself, which could readily use the right of ways. Three years later the sale was made, with the Pennsylvania paying $7.5 million for the system, which included the Main Line, the Portage Railroad, and, as it happened, the South Fork dam.
    Having no use for the dam, the railroad simply let it sit. Nothing whatsoever was done to maintain it. In fact, from 1857, the year the railroad took possession, until 1879, twenty-two years later when the Pittsburgh men took over, the dam remained more or less quietly unattended, moldering away in the woods, visited only once in a while by fishermen or an occasional deer hunter.
    And it was only five years after the state sold it to the Pennsylvania that the dam broke for the first time.
    In the late spring of 1862, about the time the Union Army under McClellan was sweating its way up the blazing Virginia peninsula, for a first big and unsuccessful drive on Richmond, the mountains of Pennsylvania were hit by heavy thunderstorms. Hundreds of tiny creeks and runs and small rivers went roaring over their banks, and in Johnstown the Tribune ran