Ulysses S. Grant (born Hiram Ulysses Grant; April 27, 1822 – July 23, 1885) was the 18th President of the United States (1869–1877) following his dominant role in the second half of the Civil War. Under Grant, the Union Army defeated the Confederate military and effectively ended the war with the surrender of Robert E. Lee's army at Appomattox. As president he led the Radical Republicans in their effort to eliminate all vestiges of Confederate nationalism and slavery; he effectively destroyed the Ku Klux Klan in 1871. His reputation was marred by his repeated defense of corrupt appointees, and by the deep economic depression (called the "Panic of 1873") that dominated his second term. Although his Republican Party split in 1872 with reformers denouncing him, Grant was easily reelected. By 1874 the opposition was gaining strength and as he left the White House in March 1877, conservative white Southerners, as federal troops were withdrawn, regained control of every state in the South and Reconstruction ended on a note of failure as the civil rights of blacks were not secure.

A career soldier, he graduated from the United States Military Academy at West Point and served in the Mexican–American War. When the Civil War began in 1861, Grant trained Union volunteer regiments in Illinois. In 1862, as a general he fought a series of battles and was promoted to major general after forcing the surrender of a large Confederate army and gaining control of Kentucky and most of Tennessee. He then led Union forces to victory after initial setbacks in the Battle of Shiloh, earning a reputation as an aggressive commander. In July 1863, after a long, complex campaign, Grant defeated five uncoordinated Confederate armies (capturing one of them) and seized Vicksburg. This famous victory gave the Union full control of the Mississippi River, split off the western Confederacy, and opened the way for more Union triumphs. After another win at the Battle of Chattanooga in late 1863, President Abraham Lincoln made him lieutenant general and commander of all of the Union Armies. As commanding general of the army, Grant confronted Robert E. Lee in a series of very bloody battles in 1864 known as the Overland Campaign that ended bottling up Lee at Petersburg, outside the Confederate capital of Richmond. During the siege, Grant coordinated a series of devastating campaigns launched by William Tecumseh Sherman, Philip Sheridan, and George Thomas. Finally breaking through Lee's trenches, the Union Army captured Richmond in April 1865. Lee surrendered his depleted forces to Grant at Appomattox as the Confederacy collapsed. Although Lee's allies denounced Grant in the 1870s as a ruthless butcher who won by brute force, most historians have hailed his military genius.