The railroads allowed greater access to the American West and its pastures and mines. Towns along railroads served as the only white settlements for hundreds of miles and provided people a place to trade and relax. Without the rails it would have been very difficult to move beef and minerals East to the growing markets there. The Transcontinental Railroad, finished in 1869 made the Oregon Trail obsolete and made it easier for people to settle on the West Coast.
Mark Twain coined the term "the Gilded Age" because it was an age of excess. To gild something means to plate it with gold--according to Twain, the financial giants of the United States such as Carnegie and Rockefeller were amassing huge profits on the backs of unskilled laborers who were barely getting by financially. Twain's moniker also had another meaning--the excess profits usually hid rotten business practices and according to Twain, corruption. Anytime there is a large discrepancy between the rich and the poor, people compare it to the Gilded Age.