The Post-Civil War Amendments (13th, 14th, and 15th) defined rights for emancipated slaves. Up to that point, the Bill of Rights only defined rights for whites in the United States. At the time of their ratification, the post-civil war amendments represented the first time slaves were accorded the rights available to all others.
So, the amendments were revolutionary in their own right! Let's briefly discuss the amendments themselves. The 13th amendment abolished slavery altogether in the United States. Interestingly, this amendment paved the way for the first civil rights bill in the United States: the Civil Rights Act of 1866.
Meanwhile, the 14th amendment established the right of slaves to be recognized as United States citizens. This amendment also prevented anyone who engaged in rebellion or insurrection against the United States to hold public office (without consent from two-thirds of Congress).
Last, but not least, the 15th amendment gave former slaves the right to vote at the local, state, and federal levels.
The post-Civil War amendments were crucial in paving the way for former slaves to access all opportunities in the economic, social, and political spheres.