Between 1870 and 1920, the American government grew exponentially in its power and reach. At the beginning of the era, the federal government was small and citizens generally governed themselves at the state and local level with little oversight from the federal government. However, towards the end of the era, the federal government would employ ten times the number of workers and exercise much greater regulatory power. Many progressives sought to secure greater power for the federal government to attempt to provide solutions to the challenges of industrialization, immigration, and urbanization. During this time, progressives would also advocate for many democratic reforms that would give citizens new ways to participate in government: initiatives, referendum, recall, party primaries, secret ballots, and the direct election of U.S. Senators through the Seventeenth Amendment. Overall, based on the belief that the American principles of limited government and limited power were outdated concepts, progressives would lay the foundations of a much larger and stronger national government that they believed could solve the problems of the twentieth century.

The late nineteenth century ushered in great changes in how the United States interacted with the rest of the world. For the first century of its existence, the United States traded with other countries, acquired territory for continental expansion, and fought in a few major wars. However, the United States was generally neutral in world affairs and focused on its domestic situation. That would change when America entered the world stage as a major global power. This expansion into world affairs led to an internal American debate regarding its international powers and responsibilities. Americans also struggled over the character of its foreign affairs—whether America would engage the world with military power or whether it would spread democracy around the world.