Abraham Lincoln (/ˈlɪŋkən/ LINK-ən; February 12, 1809 – April 15, 1865) was an American lawyer, politician, and statesman who served as the 16th president of the United States from 1861 until his assassination in 1865. Lincoln led the United States through the American Civil War, defending the nation as a constitutional union, defeating the insurgent Confederacy, abolishing slavery, expanding the power of the federal government, and modernizing the U.S. economy.

Lincoln was born into poverty in a log cabin in Kentucky and was raised on the frontier, primarily in Indiana. He was self-educated and became a lawyer, Whig Party leader, Illinois state legislator, and U.S. congressman from Illinois. In 1849, he returned to his successful law practice in Springfield, Illinois. In 1854, he was angered by the Kansas–Nebraska Act, which opened the territories to slavery, causing him to re-enter politics. He soon became a leader of the new Republican Party. He reached a national audience in the 1858 Senate campaign debates against Stephen A. Douglas. Lincoln ran for president in 1860, sweeping the North to gain victory. Pro-slavery elements in the South viewed his election as a threat to slavery, and Southern states began seceding from the nation. During this time, the newly formed Confederate States of America began seizing federal military bases in the South.