The major historical event leading to the emancipation of enslaved people in the United States was the Civil War, which began in 1861. The war was fundamentally rooted in disputes over slavery and state rights, and as it progressed, it became increasingly clear that the Union’s victory was essential for ending slavery. President Abraham Lincoln's Emancipation Proclamation, issued on January 1, 1863, declared all enslaved individuals in Confederate-held territory to be free. This pivotal action shifted the war's focus to the abolition of slavery, enabling the eventual passage of the 13th Amendment in 1865, thus formally abolishing slavery in the United States.