How did trains and railroads change life in America?

Railroads altered American society and economic life in fundamental ways. In short, they made transportation of goods and people much cheaper and quicker. They enabled the shipping of bulk goods like farm produce and coal from one end of the country to another. The railroads connected markets throughout the country, enabling the rise of a national consumer culture by the late nineteenth century based upon the consumption of common goods. It is important to remember that railroads rose roughly at the same time as the telegraph—indeed, telegraph lines were often strung along railroad right-of-way spaces—cutting the time that news, and market prices, needed to travel from one place to another. The invention of "railroad time," which eventually developed into modern-day time zones, is one example of how fundamental this change was.
Of course, the railroads also facilitated western expansion, connecting isolated western outposts to eastern metropolitan areas, and western farms to markets in places like Kansas City and Chicago. Along with railroads came mining and timber companies that depended on bulk transport, and the railroad companies often invested heavily in these operations, which frequently used lands given to railroads by the U.S. federal government. The demand for coal and especially steel created by railroad expansion was a major factor in industrial growth after the Civil War, as the country's economy became based on heavy industry. Of course, the railroads also became emblematic of the corruption and greed of the Gilded Age. "Robber barons" watered stocks, gave kickbacks, and fleeced farmers in particular in pursuit of profit. For this reason, they became a major target of the outrage of the Populist movement, and were among the first industries specifically regulated by the federal government.
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Trains and railroads dramatically changed life in America. They allowed for faster, safer travel all over the country. They were more reliable than wagon trains, as these trains could bog down in the country's terribly maintained roads. They could also move independently of livestock, which needed constant tending and forage. Railroads allowed people to send goods independently of rivers and canals. While the rails could be dangerous in terms of trains derailing or locomotives exploding, at least they did not experience flooding issues during the rainy season.
Rails were especially key in developing the West. The transcontinental railroad, when finished in 1869, gave Easterners the chance to go west for only a fraction of the price they would have paid twenty years previously. Railroads also gave Westerners the opportunity to buy Eastern goods as they could order them and have them shipped in efficiently via the rail system. Without the rail system, the nation would not be as cohesive.