On June 19, 1862, the U.S. Congress passed the Territorial Slavery Act, which outlawed slavery in all present and future federal territories of the United States. The complete and final abolition of slavery in the United States was later achieved through the Thirteenth Amendment in 1865.
The act explicitly stated that slavery or forced labor would not exist in any of the U.S. territories (the lands that did not yet have statehood, mainly in the West) except as punishment for a proven crime.
This move directly overturns the Supreme Court's infamous Dred Scott decision of 1857. Then the court ruled that Congress did not have the constitutional right to prohibit slavery in federal territories.
By signing the act, President Abraham Lincoln fulfilled a key promise from his 1860 campaign - to stop the spread of slavery outside the South so that it could gradually "die a natural death".
Congress voted and passed the legislation on June 9, 1862, and Lincoln officially signed it on June 19, 1862.
The act of June 19, 1862 was just one of many interim steps during the American Civil War. Slavery was abolished first in the federal capital of Washington, D.C., through a program of financial compensation for owners.
In June 1862, the ban extended to the western territories (such as Utah, Nebraska, and Dakota). In January In 1863, Lincoln's historic Emancipation Proclamation came into effect, declaring slaves in the territory of the seceded southern states (the Confederacy) free.
In December 1865: slavery was finally and completely banned throughout the country with the ratification of the Thirteenth Amendment to the U.S. Constitution.
The date June 19 is symbolic in American history. Three years after this law - on June 19, 1865 - Union troops reached Galveston, Texas, to declare and enforce the freedom of the last remaining black slaves in the South. Today, June 19 is celebrated as an official federal holiday in the United States, called Juneteenth (Freedom Day or Emancipation Day).