An interesting story about what stopped blackface, includes a footnote about the librarians who hid the books so that they may be found.

Barnes says the librarian admitted that, in 1987, she had personally hidden some of these books because she feared the material would be used by the Ku Klux Klan. […] When we didn’t adequately understand how long blackface was a mainstay in American culture. Because many historians believe that it had died out by 1900, when in fact it only accelerates and increases up through the 1970s. And so if you just say, “Oh, it just died out. It was no longer in fashion,” then what you’re losing is the incredible, dangerous, and brave work of thousands of Black and white mothers across the United States in the 1950s and the 1960s, of students who stood up during Jim Crow America and said, “This is not OK. We are humans. We deserve dignity. And we want you to understand our history.”