You probably want to be more careful with how you phrase that. The Republican party passed the Civil Rights Act and ended slavery, among other things.
Those may not be the type of Republicans you are thinking of today, but they still had that little (R) next to their names.
Way more Democrats in both houses of Congress voted for it than Republicans (to be fair the Democrats held the Senate 67-33). A Democratic president signed it. His Democratic predecessor asked for it. How do you figure "the Republicans did it"?
https://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964#By_pa...