I know the use of the N word went from somewhat common usage to distasteful to abhorrent in American opinion. For example, The Adventures of Huckleberry Finn(1884) portrays "nigger Jim" as humanized friend of Huck's. Did Twain use the harsh word for a friendly character as an attack on racism or did he use it because of the colloquial language of the time?
I've recently noticed that leaders in the Mormon church were still using the N word in the 1900's and I wonder how acceptable that usage would be compared to common acceptable use of the time.
For a comprehensive history of the N word, see the book by Randall Kennedy (2003). It's a good read, even though I disagree with the author's proposed solution to the problem of racial slurs (the slur itself is the title of his book).