The longest lasting victory for civil rights achieved during Reconstruction was B) Ratification of the Thirteenth, Fourteenth, and Fifteenth Amendments.
These amendments aimed to establish and protect the civil rights of African Americans: the Thirteenth Amendment abolished slavery, the Fourteenth Amendment granted citizenship and equal protection under the law, and the Fifteenth Amendment gave African American men the right to vote. While the implementation of these rights faced many challenges in the following decades, the amendments themselves remain a foundational aspect of civil rights in the United States.