Abraham Lincoln was born on February 12, 1809, in a one-room log cabin with a dirt floor on Sinking Spring Farm in Hardin County (now LaRue County), Kentucky. He was the second child of Thomas Lincoln, an illiterate farmer and carpenter, and Nancy Hanks Lincoln, joining an older sister, Sarah. In December 1816, when Lincoln was seven years old, Thomas Lincoln moved the family across the Ohio River to Spencer County in southwestern Indiana, a free state where land titles were more secure. There, young Lincoln helped his father clear timber and work the land.

In October 1818, when Lincoln was nine, his mother died of milk sickness. The following year, his father married Sarah Bush Johnston, a widow from Kentucky with three children of her own. Lincoln formed a close attachment to his stepmother, who encouraged his passion for reading despite the scarcity of books and formal schooling on the frontier; his total classroom education amounted to less than a year. As a teenager and young adult, reaching a height of six feet four inches, he worked as a farmhand and ferryboat operator, and at age 19 he piloted a flatboat loaded with farm produce down the Mississippi River to New Orleans, where he witnessed slave markets firsthand.

In March 1830, at age 21, Lincoln migrated with his extended family to Macon County, Illinois, near Decatur. After helping his father build a cabin and split fence rails, and making a second flatboat voyage to New Orleans in 1831, Lincoln struck out on his own. He settled in the river village of New Salem, Illinois, where he worked as a general store clerk, postmaster, and county surveyor. When the Black Hawk War broke out in April 1832 between the United States and Native American followers of Sauk leader Black Hawk, Lincoln volunteered for the Illinois Militia. His company elected him captain, and although he saw no combat during his three months of service, the experience boosted his local standing as he prepared to enter public life.

Lincoln ran for the Illinois House of Representatives in 1832 as a supporter of Henry Clay and the emerging Whig program of internal improvements, losing his first race before winning election in 1834 at age 25. He served four consecutive two-year terms representing Sangamon County until December 1842, becoming the Whig floor leader and championing state-funded canals, railroads, and banking. While serving in the legislature, he taught himself law by reading William Blackstone's commentaries and other legal texts, earning admission to the Illinois bar in 1836 and relocating to the new state capital of Springfield in 1837.

In Springfield, Lincoln practiced law in partnership successively with John T. Stuart, Stephen T. Logan, and, beginning in 1844, William H. Herndon. For more than two decades, Lincoln rode the Eighth Judicial Circuit each spring and autumn, handling thousands of civil and criminal cases across central Illinois and representing clients ranging from small landowners to major corporations such as the Illinois Central Railroad. His reputation for courtroom candor and plainspoken logic earned him the nickname "Honest Abe". In November 1842, he married Mary Todd, the well-educated daughter of a prominent Lexington, Kentucky, family.¹⁰ The couple purchased a two-story frame house in Springfield and had four sons: Robert Todd (born 1843), Edward Baker (1846–1850), William Wallace, known as "Willie" (1850–1862), and Thomas, known as "Tad" (1853–1871).¹¹¹² Only Robert survived to adulthood.

Elected to the U.S. House of Representatives in 1846, Lincoln served a single term from March 1847 to March 1849. As the lone Whig congressman from Illinois, he opposed the Mexican–American War, introducing his "Spot Resolutions" demanding that President James K. Polk prove that Mexican forces had shed American blood on American soil. He also supported the Wilmot Proviso to ban slavery in territory acquired from Mexico and drafted a bill for the gradual, compensated emancipation of enslaved people in the District of Columbia. Honoring an informal rotation pledge among Illinois Whigs, he did not seek re-election in 1848 and returned to his Springfield law practice.

Lincoln remained largely out of politics for five years until Democratic Senator Stephen A. Douglas of Illinois shepherded the Kansas–Nebraska Act through Congress in May 1854.¹³ The law repealed the Missouri Compromise of 1820, which had prohibited slavery north of the 36°30′ parallel, and replaced it with "popular sovereignty," allowing white settlers in new territories to vote on whether to permit slavery. Alarmed by the prospect of slavery's indefinite expansion, Lincoln delivered his October 1854 Peoria speech, arguing that slavery violated the foundational principles of the Declaration of Independence and that the Founding Fathers had intended to place the institution on the path to ultimate extinction.¹⁴

Before Lincoln took office on March 4, 1861, seven Deep South states—South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas—declared their secession from the Union and formed the Confederate States of America under Jefferson Davis. In his First Inaugural Address, Lincoln pledged not to interfere with slavery where it already existed, declared secession legally void, and appealed to the bonds of national affection while affirming his constitutional duty to hold federal property. When Lincoln attempted to resupply the besieged federal garrison at Fort Sumter in Charleston Harbor, South Carolina, Confederate artillery opened fire on April 12, 1861, forcing the fort's surrender.

On April 15, Lincoln called for 75,000 militia volunteers to suppress the rebellion and ordered a naval blockade of Confederate ports. In response, four Upper South states—Virginia, Arkansas, North Carolina, and Tennessee—joined the Confederacy, while Lincoln combined political persuasion and military pressure to keep the four slaveholding border states of Delaware, Maryland, Kentucky, and Missouri within the Union. To unite the Northern war effort, he assembled a cabinet that included his chief Republican rivals: William H. Seward as secretary of state, Salmon P. Chase as secretary of the treasury, Simon Cameron (replaced in January 1862 by Edwin M. Stanton) as secretary of war, and Edward Bates as attorney general.

Beyond the war effort, Lincoln and the Republican-controlled 37th Congress enacted a legislative program that reshaped the American economy and expanded the reach of the federal government.²⁹ In May 1862, Lincoln signed the Homestead Act, which granted 160 acres of western public land to any adult citizen or intended citizen—including unmarried women and formerly enslaved people—who paid a modest filing fee and improved the property for five years.³⁰³¹ He also created the U.S. Department of Agriculture in May 1862, calling it the "People's Department."

On July 1, 1862, Lincoln signed the Pacific Railway Act, providing federal land grants and government bonds to the Union Pacific and Central Pacific railroads to construct the nation's first transcontinental railroad along a northern route connecting Omaha, Nebraska, and Sacramento, California.³² The following day, July 2, 1862, he signed the Morrill Land-Grant Colleges Act, donating 30,000 acres of federal land per congressional representative to each state to fund public universities dedicated to agriculture and the mechanical arts. To finance the war, his administration instituted the first federal income tax under the Revenue Act of 1861, issued paper currency known as "greenbacks" under the Legal Tender Act of 1862, and established a uniform national banking system through the National Banking Acts of 1863 and 1864. Lincoln also established Thanksgiving as a regular national holiday in October 1863.

In foreign policy, Lincoln and Secretary of State Seward worked to prevent the United Kingdom and France from granting diplomatic recognition to the Confederacy or breaking the Union blockade to secure Southern cotton. When a U.S. Navy warship intercepted the British mail packet RMS Trent in November 1861 and seized two Confederate envoys, James Mason and John Slidell, Britain threatened war. Lincoln defused the Trent Affair by ordering the envoys released, famously remarking, "One war at a time." The issuance of the Emancipation Proclamation further discouraged European intervention by aligning the Union cause with British and French anti-slavery public opinion.

Lincoln's expansive exercise of executive power during the Civil War provoked intense debate during his lifetime and among constitutional scholars ever since.³³ On April 27, 1861, while Congress was out of session and Confederate sympathizers in Maryland were sabotaging rail and telegraph lines to Washington, Lincoln suspended the writ of habeas corpus along the corridor between Washington, D.C., and Philadelphia.³⁴ When military authorities arrested Maryland secessionist John Merryman and held him at Fort McHenry, Chief Justice Roger B. Taney, sitting as a federal circuit judge in Ex parte Merryman (1861), ruled that only Congress had the constitutional authority under Article I, Section 9 to suspend the writ.³⁵

Lincoln defied Taney's ruling, arguing in a July 4, 1861, message to Congress that the Constitution permitted suspension in cases of rebellion without specifying which branch should act, and asking, "Are all the laws, but one, to go unexecuted, and the government itself go to pieces, lest that one be violated?" In September 1862, Lincoln expanded the suspension nationwide for anyone resisting the draft or aiding the rebellion, a measure Congress formally authorized through the Habeas Corpus Suspension Act of March 1863. Over the course of the war, Union military authorities arrested at least 13,000 civilians—including smugglers, blockade runners, draft resisters, and Peace Democrats ("Copperheads") such as former Ohio Congressman Clement Vallandigham—and tried many before military tribunals. While critics then and later characterized these actions as executive overreach or "constitutional dictatorship," defenders note that most detainees were held briefly in border war zones and that Lincoln preserved competitive elections in 1862 and 1864.

Historians have also scrutinized Lincoln's evolving views on race and his administration's policies toward Native Americans.³⁶ For much of his career, up until late 1862, Lincoln supported voluntary colonization—resettling freed African Americans in Central America, the Caribbean, or Liberia—out of pessimism that white Americans would ever accept peaceful biracial coexistence, a view he abandoned after the Emancipation Proclamation and the service of Black Union troops. In the West, broken federal treaty annuity payments and settler encroachment triggered the Dakota War of 1862 in Minnesota, in which hundreds of white settlers and soldiers were killed.³⁷³⁸ After a rushed military commission sentenced 303 Dakota men to death, Lincoln ordered a personal review of the trial transcripts to distinguish between those who had participated in warfare and those convicted of massacring or raping civilians.³⁹ Resisting fierce pressure from Minnesota officials to execute all 303, Lincoln commuted the sentences of 264 men and approved the execution of 39 (one was later reprieved). The hanging of 38 Dakota men at Mankato, Minnesota, on December 26, 1862, remains the largest single-day mass execution in United States history.

On April 9, 1865, Confederate General Robert E. Lee surrendered the Army of Northern Virginia to Ulysses S. Grant at Appomattox Court House, effectively ending major combat in the Civil War. Two days later, on April 11, speaking from a White House window, Lincoln delivered his final public address, in which he endorsed voting rights for educated African Americans and Black Union veterans—the first time an American president publicly supported Black suffrage. In the audience was John Wilkes Booth, a well-known stage actor and ardent Confederate sympathizer, who vowed that it would be the last speech Lincoln ever made.

On the evening of Good Friday, April 14, 1865, Lincoln and Mary Todd Lincoln attended a performance of the comedy Our American Cousin at Ford's Theatre in Washington, D.C., accompanied by Major Henry Rathbone and Clara Harris.⁴⁰ At approximately 10:15 p.m., Booth entered the unguarded presidential box from behind and fired a single .44-caliber Derringer pistol ball into the back of Lincoln's head, before slashing Rathbone with a dagger and leaping onto the stage. The attack was part of a broader conspiracy in which accomplice Lewis Powell severely wounded Secretary of State Seward at his home, while George Atzerodt failed to carry out an assigned attack on Vice President Andrew Johnson.⁴¹ Unconscious, Lincoln was carried across Tenth Street to the Petersen House, where he died the following morning, April 15, 1865, at 7:22 a.m. at the age of 56. Booth was tracked down and fatally shot by Union soldiers in a Virginia barn on April 26, and four co-conspirators—Powell, Atzerodt, David Herold, and Mary Surratt—were tried by a military commission and hanged on July 7, 1865.⁴²

Following funeral services in Washington, a funeral train carried Lincoln's body along a 1,654-mile route through seven states to Springfield, Illinois, viewed by millions of mourners before his interment at Oak Ridge Cemetery. His martyrdom at the moment of Union victory cemented his stature as the "Great Emancipator" and the savior of the American republic. In historical rankings of U.S. presidents conducted among scholars and the public, Lincoln has consistently ranked first or among the top three alongside George Washington and Franklin D. Roosevelt. His image is commemorated on the United States one-cent coin and five-dollar bill, at Mount Rushmore in South Dakota, and at the Lincoln Memorial on the National Mall in Washington, D.C., dedicated in 1922, which became an enduring staging ground for the American civil rights movement.