The Central Pacific, meanwhile, continued to drive eastward. Its Chinese laborers - initially recruited when new silver mines lured other workers - had learned quickly, pushing rails eastward through the mountains and across the Nevada desert to Utah's western border by 1869. When Charles Crocker, CP's construction boss, heard that Union Pacific crews had topped his previous record by laying 8 miles of track in one day, he bet $10,000 on the ability of his own crews. The Chinese workers, he said, could lay 10 miles of rail 'between daylight and dark.' After careful planning, his crews swung into action, laying 10 miles and 56 feet in less than 12 hours.

Finally, on May 10, 1869, Central Pacific and Union Pacific locomotives sat a shovel toss of coal apart at Promontory, Utah, just north of the Great Salt Lake. Plans for heroic joining had been laid well ahead of time and photographers were on hand to record this historic moment in U.S. history. The Central Pacific president and former Governor of California, Leland Stanford, would join the Union Pacific Vice President Thomas Durant in driving home a final gold spike with a silver sledge hammer.

It had taken more than half a century from the time the nation's first railroad was chartered to build a transcontinental railroad. It took only 12 more years to build the second, this one coming to a junction in New Mexico and providing the first direct line to southern California. Two years later, St. Paul was linked to the Pacific Northwest, and New Orleans got a connection to the West Coast.

The system grew rapidly after that. Five more years saw the completion of a southern route between California and Chicago. The Atchison, Topeka & Santa Fe met the Southern Pacific in 1881, and finished its own route to the coast across New Mexico and Arizona in 1883.

Meanwhile, the Denver, Rio Grande & Western became the defacto 'trunk line' of the Colorado, Utah and New Mexico region. Founded in 1870, the railroad built a vast and intricate network throughout the ore-rich mining country of the Rockies of Colorado and the adjacent states. One of America's smaller roads, the Denver Rio Grande & Western remains in service to this day, as both a freight and passenger road - one of the last.