The US Constitution committed to equality in the Thirteenth, Fourteenth, and Fifteenth Amendments following the Civil War. Legislators and judges quickly confronted the question of what these new provisions might mean for private actors. The Radical Republicans aimed to bring the commitment to equal protection into private spaces, propagating republican discourses about the practical requirements of equal citizenship and the potential duties of private actors. However, the Supreme Court soon reached its own countervailing conclusion that only state actors, not private actors, gained duties from the Reconstruction Amendments. While this latter understanding remained firm, private actors effectively gained obligations to equality under the Civil Rights Act of 1964 and later court decisions working around the initial cabining of constitutional equality. Later debates evince a revival of republican-inflected language and arguments for something like horizontal application, even while the country’s jurists viewed such an extension of rights as basically impossible. Several other episodes in constitutional politics, both at the national and state levels, would continue to revisit this question across a range of issue areas.