Ulysses S. Grant (born Hiram Ulysses Grant HY-rm yoo-LISS-eez; April 27, 1822 July 23, 1885) was an American military officer and politician who served as the 18th president of the United States from 1869 to 1877. As Commanding General, he led the Union Army to victory in the American Civil War in 1865 and thereafter briefly served as Secretary of War. Later, as president, Grant was an effective civil rights executive who signed the bill that created the Justice Department and worked with Radical Republicans to protect African Americans during Reconstruction.

Raised in Ohio, Grant possessed an exceptional ability with horses. Admitted to West Point, Grant graduated 21st in the class of 1843 and served with distinction in the MexicanAmerican War. In 1848, he married Julia Dent, and together they had four children. Grant resigned from the army in 1854 and returned to his family but lived in poverty. He joined the Union Army after the American Civil War broke out in 1861 and rose to prominence after winning several early Union victories on the Western Theater. In 1863 he led the Vicksburg campaign, which gained control of the Mississippi River, dealing a serious strategic blow to the Confederacy, splitting it in two. President Abraham Lincoln promoted him to lieutenant general after his victory at Chattanooga. For thirteen months, Grant fought Robert E. Lee during the high-casualty Overland Campaign and at Petersburg. After Lee fled Petersburg, Grant defeated him at Appomattox. On April 9, 1865, Lee formally surrendered to Grant. A week later, Lincoln was assassinated and was succeeded by President Andrew Johnson, who promoted Grant to General of the Army in 1866. Later, Grant openly broke with Johnson over Reconstruction policies; Grant used the Reconstruction Acts, which had been passed over Johnson's veto, to enforce civil rights for recently freed African Americans.

A war hero, drawn in by his sense of duty, Grant was unanimously nominated by the Republican Party and was elected president in 1868. As president, Grant stabilized the post-war national economy, supported Congressional Reconstruction, ratification of the 15th Amendment, and crushed the Ku Klux Klan. Under Grant, the Union was completely restored. He appointed African Americans and Jewish Americans to prominent federal offices. In 1871, Grant created the first Civil Service Commission, advancing the civil service more than any prior president. The Liberal Republicans and Democrats united behind Grant's opponent in the presidential election of 1872, but Grant was handily reelected. Grant's Native American policy was to assimilate Indians into White culture; the Great Sioux War was fought during his term. Grant's foreign policy was mostly peaceful, without war, the Alabama Claims against Great Britain skillfully resolved. However, his prized Caribbean Dominican Republic annexation was rejected by the Senate.

The Grant administration is traditionally known for prevalent scandals including the Gold Ring and the Whiskey Ring. However, modern scholarship has better appreciated Grant's appointed reformers and prosecutions. Grant appointed John Brooks Henderson and David Dyer, who prosecuted the Whiskey Ring. Grant appointed Benjamin Bristow and Edwards Pierrepont, who served as Grant's anti-corruption team. Grant appointed Zachariah Chandler, who cleaned up corruption in the Interior. Grant's administration prosecuted Mormon polygamists (1871), and vice crimes like pornography, and abortion (18731877). The Panic of 1873 plunged the nation into a severe economic depression that allowed the Democrats to win the House majority. In the intensely disputed presidential election of 1876, Grant facilitated the approval by Congress of a peaceful compromise.

In his retirement, Grant was the first president to circumnavigate the world on his tour, dining with Queen Victoria and meeting many prominent foreign leaders. In 1880, Grant was unsuccessful in obtaining the Republican presidential nomination for a third term. In the final year of his life, facing severe financial reversals and dying of throat cancer, he wrote his memoirs, which proved to be a major critical and financial success. At the time of his death, he was memorialized as a symbol of national unity. Grant was a modern general and "a skillful leader who had a natural grasp of tactics and strategy".

Historical assessments have often ranked Grant as one of the worst presidents in American history. However, revisionist challenges to this narrative have received significant support in recent times. Although critical of scandals, modern historians have emphasized his presidential administration's accomplishments. These included the prosecution of the Klan, treatment of Black people as both human and American, an innovative Native American policy, and the peaceful settlements of the Alabama Claims and controversial 1876 presidential election. Grant's appointment of Hamilton Fish as Secretary of State is ranked high by historians.

The American Civil War (April 12, 1861 – May 9, 1865; also known by other names) was a civil war in the United States between the Union (states that remained loyal to the federal union, or "the North") and the Confederacy (states that voted to secede, or "the South"). The central cause of the war was the status of slavery, especially the expansion of slavery into territories acquired as a result of the Louisiana Purchase and the Mexican–American War. On the eve of the Civil War in 1860, four million of the 32 million Americans (~13%) were enslaved black people, almost all in the South.The practice of slavery in the United States was one of the key political issues of the 19th century. Decades of political unrest over slavery led up to the Civil War. Disunion came after Abraham Lincoln won the 1860 United States presidential election on an anti-slavery expansion platform. An initial seven southern slave states declared their secession from the country to form the Confederacy. Confederate forces seized federal forts within territory they claimed. The last-minute Crittenden Compromise tried to avert conflict but failed; both sides prepared for war. Fighting broke out in April 1861 when the Confederate army began the Battle of Fort Sumter in South Carolina, just over a month after the first inauguration of Abraham Lincoln. The Confederacy grew to control at least a majority of territory in eleven states (out of the 34 U.S. states in February 1861), and asserted claims to two more. Both sides raised large volunteer and conscription armies. Four years of intense combat, mostly in the South, ensued.

During 1861–1862 in the war's Western Theater, the Union made significant permanent gains—though in the war's Eastern Theater the conflict was inconclusive. On January 1, 1863, Lincoln issued the Emancipation Proclamation, which made ending slavery a war goal, declaring all persons held as slaves in states in rebellion "forever free." To the west, the Union destroyed the Confederate river navy by the summer of 1862, then much of its western armies, and seized New Orleans. The successful 1863 Union siege of Vicksburg split the Confederacy in two at the Mississippi River. In 1863, Confederate General Robert E. Lee's incursion north ended at the Battle of Gettysburg. Western successes led to General Ulysses S. Grant's command of all Union armies in 1864. Inflicting an ever-tightening naval blockade of Confederate ports, the Union marshaled resources and manpower to attack the Confederacy from all directions. This led to the fall of Atlanta in 1864 to Union General William Tecumseh Sherman and his march to the sea. The last significant battles raged around the ten-month Siege of Petersburg, gateway to the Confederate capital of Richmond.

The Civil War effectively ended on April 9, 1865, when Confederate General Lee surrendered to Union General Grant at the Battle of Appomattox Court House, after Lee had abandoned Petersburg and Richmond. Confederate generals throughout the Confederate army followed suit. The conclusion of the American Civil War lacks a clean end date: land forces continued surrendering until June 23. By the end of the war, much of the South's infrastructure was destroyed, especially its railroads. The Confederacy collapsed, slavery was abolished, and four million enslaved black people were freed. The war-torn nation then entered the Reconstruction era in a partially successful attempt to rebuild the country and grant civil rights to freed slaves.

The Civil War is one of the most studied and written about episodes in the history of the United States. It remains the subject of cultural and historiographical debate. Of particular interest is the persisting myth of the Lost Cause of the Confederacy. The American Civil War was among the earliest to use industrial warfare. Railroads, the telegraph, steamships, the ironclad warship, and mass-produced weapons saw wide use. In total the war left between 620,000 and 750,000 soldiers dead, along with an undetermined number of civilian casualties. President Lincoln was assassinated just five days after Lee's surrender. The Civil War remains the deadliest military conflict in American history. The technology and brutality of the Civil War foreshadowed the coming World Wars.