In 1863 Republicans freed the slaves.
On New Year's Day in 1863, the Republican Party's Emancipation Proclamation came into effect. While Republicans rejoiced, Democrat politicians and newspapers denounced President Abraham Lincoln (R-IL) for freeing slaves.
The Republican Party was founded primarily to oppose slavery, and Republicans eventually abolished slavery. The Democratic Party fought them and tried to maintain and expand slavery. The 13th Amendment, abolishing slavery, passed in 1865 with 100% Republican support but only 23% Democrat support in congress.
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American Slavery, American Freedom
A People's History of the United States