Ulysses S. Grant - General Grant led the Army of Tennessee in the early stages of the war. He claimed early victories at Fort Henry and Fort Donelson earning the nickname "Unconditional Surrender." After winning major victories at Shiloh and Vicksburg, Grant was promoted by President Lincoln to lead the entire Union Army. Grant led the Army of the Potomac into several battles against Confederate General Robert E. Lee and eventually accepted his surrender at the Appomattox Court House.
George McClellan - General McClellan was appointed head of the Union Army of the Potomac after the First Battle of Bull Run. McClellan turned out to be a timid general. He always thought he was outnumbered when, in fact, his army was usually much larger than the Confederate army. McClellan led the Union Army at the Battle of Antietam, but refused to pursue the Confederates after the battle and was relieved of his command.
William Tecumseh Sherman by Matthew Brady
William Tecumseh Sherman - General Sherman led under Grant at the Battle of Shiloh and the Siege of Vicksburg. He then gained command of his own army and conquered the city of Atlanta. He is most famous for his "march to the sea" from Atlanta to Savannah where he destroyed everything that could be used against his army along the way.
Joseph Hooker - General Hooker commanded at several major Civil War battles including the Battle of Antietam and the Battle of Fredericksburg. After Fredericksburg he was put in command of the entire Army of the Potomac. He didn't hold this position very long as he soon suffered a heavy defeat at the Battle of Chancellorsville. He was removed from command by Abraham Lincoln shortly before the Battle of Gettysburg.
Winfield Scott Hancock - General Hancock was considered one of the most talented and brave commanders in the Union Army. He commanded at several major battles including the Battle of Antietam, the Battle of Gettysburg, and the Battle of Spotsylvania Court House. He is most famous for his bravery and leadership at the Battle of Gettysburg.
George Henry Thomas by Matthew Brady
George Thomas - General Thomas is considered by many to be one of the top Union generals of the Civil War. He won several important victories in the western theatre of the war. He is most famous for his stout defense at the Battle of Chickamauga which earned him the nickname "the Rock of Chickamauga." He also led the Union to a major victory at the Battle of Nashville.
Robert E. Lee - General Lee led the Confederate Army of Virginia throughout the Civil War. He was a brilliant commander who won many battles while being greatly outnumbered. His most important victories include the Second Battle of Bull Run, the Battle of Fredericksburg, and the Battle of Chancellorsville.
Jeb Stuart by Unknown
Stonewall Jackson - General Jackson earned his nickname "Stonewall" early in the war at the First Battle of Bull Run. When his soldiers held firmly against a fierce Union attack, it was said
that he stood like a "stone wall." Jackson was known for his fast moving "foot cavalry" and his aggressive command. He won several battles in the Shenandoah Valley during the Valley Campaign. Jackson was accidentally killed by his own men at the Battle of Chancellorsville.
J.E.B. Stuart - General Stuart (known as "Jeb") was the top cavalry commander for the Confederacy. He fought in many battles including the First Battle of Bull Run, the Battle of Fredericksburg, and the Battle of Chancellorsville. Although he was known as a gifted commander, he made a mistake during the Battle of Gettysburg that may have cost the Confederacy the battle. Stuart was killed at the Battle of Yellow Tavern.
P.G.T. Beauregard - General Beauregard led the South in capturing Fort Sumter in the first battle of the Civil War. He later fought in battles at Shiloh and Bull Run. He is most known for holding off Union forces at St. Petersburg long enough for reinforcements from Robert E. Lee to arrive.
Joseph Johnston by Unknown
Joseph Johnston - General Johnston led the Confederates to their first major victory in the Civil War at the First Battle of Bull Run. However, he did not get along well with Confederate President Jefferson Davis. Johnston suffered some major defeats while commanding the Confederate army in the west including Vicksburg and Chickamauga. He surrendered his army to Union General Sherman at the end of the war.