On May 10, 1869, a golden spike was driven into a railroad tie at Promontory Summit, Utah. This single act connected the east and west coasts of the United States by rail for the first time. Before the railroad, crossing the country took four to six months by wagon or ship. The new train could make the trip in about six days. The railroad was built by two companies working toward each other. The Central Pacific started in Sacramento, California, and built eastward. The Union Pacific started in Omaha, Nebraska, and built westward. Together, they laid nearly 1,800 miles of track. The work was incredibly difficult. Workers blasted through granite mountains, built bridges across deep canyons, and laid track through scorching deserts. Chinese immigrants made up most of the Central Pacific workforce, while Irish immigrants and Civil War veterans made up much of the Union Pacific's. The railroad transformed American geography in practical ways. Goods that once took months to ship could now arrive in days. Settlers moved west in huge numbers. New towns sprang up along the rail lines. The railroad also led to the creation of standard time zones because trains needed a reliable schedule across the country.