Answer:
After the civil war, the United States began a rapid process of industrialization, and by the end of the century, it was the world's leading industrial nation.
This industrialization process was possible because of the many technological advancements of the era: the telegraph, the railroad, electricity, steel manufacturing, etc, and also, thanks to the abundance of natural resources in the country: coal, iron ore, oil and abundant farmland.
Factory labor came from both local population and immigrants. From the mid-nineteenth century to the first decades of the twentieth century, around 27 seven million immigrants arrived in the United States, the vast majority from Europe, especially from Germany, Italy and Ireland.
The Germans mostly became farmers, while the Italians and the Irish stayed in the cities and became industrial workers. Another source of labor force were African Americans, who began to migrate from the South to the industrial North after they earned their freedom.
Labor conditions were hard for most people, especially in cities. Many immigrants lived in ethnic enclaves or ghettoes. Poverty and disease were common.
The progressives were a movement who worked to solve these problem sfrom the late 19th century. They sought to reform the laws, modernize the federal government, and end corruption. Worker's unions also formed and fought for labor rights, but many of them were suppressed, sometimes violently.
