There was a time when traveling from the East Coast to the West Coast meant riding for months in a horse-drawn wagon or stagecoach, or sailing southward to Panama and then crossing the Isthmus to board another ship for a journey up the other coast. But that all changed on May 10, 1869, when railroad baronLeland Stanford whacked in a ceremonial gold spike to mark the joining together of the tracks of the Central Pacific Railroad and the Union Pacific Railroad in Promontory, Utah, to form the transcontinental railroad. The new rail connection eventually made it possible to travel in a train car from New York to San Francisco in just a week’s time.

Some 21,000 workers—from Irish-American Civil War veterans, freed slaves and Mormon pioneers to Chinese laborers—had been recruited to perform the hard and often dangerous work of laying the 1,776 miles of track. By one estimate, the project cost roughly $60 million, about $1.2 billion in today’s money, though other sources put the amount even higher.

While the railroad's construction was a mammoth undertaking, its effects on the country were equally profound. Here are some of the ways that the first transcontinental railroad—and the many other transcontinental lines that followed it—changed America.