Modern Marvels: On a somber day in Gettysburg, Abraham Lincoln ended his famous address with a promise that the war-torn nation would be reborn. The greatest symbol of that rebirth had already begun, hailed as an engineering feat to rival the pyramids the construction of the Transcontinental Railroad. Its construction was an engineering marvel and a technological nightmare. The Union Pacific built westward from Omaha, and the Central Pacific eastward from Sacramento, hoping they would someday meet. The work crept inch by grueling inch across the forbidding continent and the treacherous Sierras. Here is the epic tale of the struggle to forge an iron link across the untamed West, and the only engineering feat to spawn an American folk tale: the legend of John Henry. After a decade of work, on May 10, 1869 at Promontory, Utah, as the last symbolic spike linking the two railways was driven, a nation was united and forever transformed.