Final answer:
The 'act' that Abraham Lincoln put into effect on January 1, 1863, to free all slaves in the Confederate states was known as the Emancipation Proclamation. It was a significant move towards ending slavery, leading to the Thirteenth Amendment, which abolished slavery throughout the entire United States.
Step-by-step explanation:
On January 1, 1863, President Abraham Lincoln issued the Emancipation Proclamation, an act that declared all slaves in Confederate states in rebellion against the United States to be free. The proclamation was limited in direct effect, as it applied only to territories not under Union control.
Nonetheless, it was a critical step towards the abolition of slavery and paved the way for the ratification of the Thirteenth Amendment, which formally abolished slavery throughout the United States in December 1865.