It was an era of corporate consolidation, especially in the steel, rail, oil, and telecommunications industries. Monopolies denied competition in the marketplace, which led to calls for government regulation. A law was passed in 1890 to prevent monopolies from restraining trade, but it was not vigorously enforced at first.

Even with the great gains in industry, farming remained America's basic occupation. Yet it, too, witnessed enormous changes. Farmland doubled and scientists developed improved seeds. Machines — including mechanical planters, reapers, and threshers — took over much of the work that had previously been done by hand. American farmers produced enough grain, cotton, beef, pork, and wool to supply the growing domestic market and still have large surpluses to export.

The western region of the United States continued to attract settlers. Miners staked claims in the ore-rich mountains, cattle ranchers on the vast grasslands, sheep farmers in the river valleys, and farmers on the great plains. Cowboys on horses took care of the animals and guided them to distant railroads for shipment east. This is the image of America that many people still have, even though the era of the "Wild West" cowboy lasted only about 30 years.

From the time that Europeans landed on the east coast of America, their migration westward meant confrontation with native peoples. For many years, government policy had been to move Native Americans beyond the reach of the white frontier to lands reserved for their use. Time and again, however, the government ignored its agreements and opened these areas to white settlement. In the late 1800s, Sioux tribes in the northern plains and Apaches in the southwest fought back hard to preserve their way of life. They were skilled fighters but were eventually overwhelmed by government forces. Official policy after these conflicts was well-intentioned but sometimes proved disastrous. In 1934, Congress passed a measure that attempted to protect tribal customs and communal life on the reservations.

The last decades of the 19th century saw a race by European powers to colonize Africa and compete for trade in Asia. Many Americans believed the United States had a right and duty to expand its influence in other parts of the world. Many others, however, rejected any actions that hinted at imperialism.

A brief war with Spain in 1898 left the United States with control over several Spanish overseas possessions: Cuba, Puerto Rico, Guam, and the Philippines. Officially, the United States encouraged them to move toward self-government, but, in fact, it maintained administrative control. Idealism in foreign policy existed alongside the practical desire to protect the economic interests of a once-isolated nation that had become a world power.