The United States started the long process of industrializing in the late 1700s, though the process increased exponentially after the Civil War in the 1860s, a period often referred to as the "second Industrial Revolution." The foundation of the industrialization process was the improvement of modes of transportation, including railroads and canals, that vastly sped up the delivery of goods to consumers, along with an improvement in technology such as the making of steel. While this question has several answers, historians generally agree that industrialization improved the standard of living for many Americans, even as the working classes continued to struggle with poor working conditions.
Before the Industrial Revolution, Americans were largely dependent on farming, and, as a result, they often relied on an inconsistent source of income. Although conditions in many factories were dangerous, workers benefited from a consistent source of income. Those who were able to find managerial positions in factories and related fields formed a burgeoning middle class, and life expectancy and wages improved steadily after the Civil War (until the Great Depression of the 1930s). Many new professions developed during this time period, including law, engineering, and accounting.
The middle class was able to use the disposable income they made (that is, money that they did not need for necessities such as housing and food) to purchase goods that made them more comfortable and gave them access to entertainment, including sports, theatre, books, and other forms of entertainment. People who had time that they did not need to dedicate to working on the farm also were able to devote themselves to bettering themselves through education and through reform movements, including temperance, women's rights, and other causes. Though working conditions were still poor during this time period, the standard of living improved for many Americans.