Following the Civil War, settlers began to move west. Miners, ranchers, and farmers settled on the Great Plains, despite resistance from Native Americans. The railroads, the soil and climate, and land laws such as the Homestead Act encouraged settlement of the Plains. This expansion resulted in the slaughter of vast numbers of buffaloes on the Plains, an animal on which the Native American way of life was dependent. Conflict arose as the federal government tried to move Native Americans from their homelands to reservations.
At the same time that many settlers were moving west, others moved to the cities. The United States was changing from a rural nation into a modern, industrial nation. Rich natural resources, the growth of the railroads, and an invention boom spurred the industrialization of the country. Cities also grew at this time because of immigrants. After the Civil War, many immigrants arrived from southern and eastern Europe as well as from China, Japan, and Mexico. Many of them settled in cities and looked for work. During the 1880s and 1890s reformers began to campaign to deal with city problems such as overcrowding, crime, and poor sanitation.
The progressive movement of the early 1900s grew out of the reform movements of the previous decades. Progressives sought to control unfair business practices and expand democracy. Others fought for woman suffrage, or women's right to vote, which was finally granted in 1920 by the Nineteenth Amendment. African Americans and Mexican Americans also worked for greater equality.
A spirit of imperialism emerged among the world's countries in the late 1800s and early 1900s. This, along with feelings of nationalism, led to tensions that erupted into world war in 1914. World War I pitted the Allies—Great Britain, France, Russia, and the United States—against the Central Powers—Germany, Austria-Hungary, and the Ottoman Empire. After the Allies won the long, difficult war, Americans were ready to seek enjoyment at home. The 1920s were a time of new pastimes and recreation as the nation enjoyed a booming post-war economy.