American Civil War: The Battle of Shiloh begins: In Tennessee, forces under Union General Ulysses S. Grant meet Confederate troops led by General Albert Sidney Johnston.

The American Civil War was a civil war in the United States between the Union and the Confederacy, which was formed in 1861 by states that had seceded from the Union. The central conflict leading to war was a dispute over whether slavery should be permitted to expand into the western territories, leading to more slave states, or be prohibited from doing so, which many believed would place slavery on a course of ultimate extinction.

The Battle of Shiloh, also known as the Battle of Pittsburg Landing, was a major battle in the American Civil War fought on April 6–7, 1862. The fighting took place in southwestern Tennessee, which was part of the war's Western Theater. The battlefield is located between a small, undistinguished church named Shiloh and Pittsburg Landing on the Tennessee River. Two Union armies combined to defeat the Confederate Army of Mississippi. Major General Ulysses S. Grant was the Union commander, while General Albert Sidney Johnston was the Confederate commander until his battlefield death, when he was replaced by his second-in-command, General P. G. T. Beauregard.

Tennessee, officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina to the east, Georgia, Alabama, and Mississippi to the south, Arkansas to the southwest, and Missouri to the northwest. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. According to the United States Census Bureau, the state's estimated population as of 2024 is 7.22 million.

The Union was the central government of the United States during the American Civil War. Its civilian and military forces resisted the Confederacy's attempt to secede following the election of Abraham Lincoln as president of the United States. Lincoln's administration asserted the permanency of the federal government and the continuity of the United States Constitution.