The statement that is true of the Emancipation Proclamation is: It freed all slaves in the states rebelling against the Union.
The Emancipation Proclamation, issued by President Abraham Lincoln on January 1, 1863, declared that all slaves in the Confederate states (those that were in rebellion against the Union) were to be set free. However, it did not grant U.S. citizenship or voting rights to freedmen and freedwomen, nor did it outlaw slavery in the entire United States; that would not occur until the ratification of the 13th Amendment in December 1865.