CIVILWAR & INDUSTRIALISATION OF USA

Battle of Gettysburg, lithograph by Currier & Ives, ca. 1863Tensions between slave and free states mounted with arguments over the relationship between the state and federal governments, as well as violent conflicts over the spread of slavery into new states.Abraham Lincoln, candidate of the largely antislavery Republican Party, was elected president in 1860.

Before he took office, seven slave states declared their secession—which the federal government maintained was illegal—and formed the Confederate States of America. With the Confederate attack upon Fort Sumter, the American Civil War began and four more slave states joined the Confederacy. Lincoln's Emancipation Proclamation committed the Union to ending slavery.

Following the Union victory in 1865, three amendments to the U.S. Constitution ensured freedom for the nearly four million African Americans.The resolution of the disputed 1876 presidential election by the Compromise of 1877 ended Reconstruction; Jim Crow laws soon disenfranchised many African Americans. In the North, urbanization and an unprecedented influx of immigrants from Southern and Eastern Europe hastened the country's industrialization.

World War I, Great Depression, and World War IIMain articles: American Expeditionary Force, Great Depression in the United States, and Military history of the United States during World War II An abandoned farm in South Dakota during the Dust Bowl, 1936At the outbreak of World War I in 1914, the United States remained neutral. Most Americans sympathized with the British and French, although many opposed intervention.