The correct answer is: "The Civil Rights Act".
Although equality of rights for all US citizens had been already included in the US Constitution during the Reconstruction era, through the enactment of the 13th, 14th and 15th Amendments in 1865, 1868 and 1870 respectively, such equality did not happen in practice until one century later, after the preassure exercised by the Civil Rights Movement, with the enactment of the Civil Rights Act.
The Civil Rights Act was enacted in 1964 forbids discrimination in terms of race, color, religion, sex, or national origin. Moreover, these principles were translated into provisions that aimed to rule out such discrimination also in the practice: eliminating requirements in order to access voting, banning segregation in schools, public facilities and employment. etc.
