Abraham Lincoln served as the 16th President of the United States from March 1861 until his assassination in April 1865. He successfully led the country through its greatest internal crisis, the American Civil War, preserving the Union, ending slavery, and rededicating the nation to nationalism, equal rights, liberty, and democracy. Reared in a poor family on the western frontier, he was mostly self-educated and became a country lawyer, an Illinois state legislator, and a one-term member of the United States House of Representatives, but failed in two attempts at a seat in the United States Senate. He was an affectionate, though often absent, husband, and father of four children.

As an outspoken opponent of the expansion of slavery in the United States, Lincoln won the first Republican nomination and was elected president in 1860. His Gettysburg Address of 1863, although short, became one of the most quoted speeches in history. It became an iconic statement of America's dedication to the principles of nationalism, equal rights, liberty, and democracy. He issued his Emancipation Proclamation in 1863, and promoted the passage of the Thirteenth Amendment to the United States Constitution, abolishing slavery.

At the close of the war, Lincoln held a moderate view of Reconstruction, seeking to speedily reunite the nation through a policy of generous reconciliation. Six days after the surrender of the main Confederate forces, Lincoln was assassinated, the first President to suffer such a fate. Lincoln has consistently been ranked by scholars as one of the greatest U.S. Presidents.