The major event in U.S. history that took place at Gettysburg in 1863 was the Battle of Gettysburg, a crucial turning point in the American Civil War. It was fought from July 1 to July 3 and marked the most significant and bloodiest battle of the conflict, resulting in over 50,000 casualties. The Union victory halted General Robert E. Lee's invasion of the North and strengthened Northern morale. The battle's aftermath, coupled with President Abraham Lincoln’s Gettysburg Address, underscored the war's broader implications regarding national unity and the principles of liberty and equality. This event significantly shaped the course of American history and post-war national identity.