Pre-Civil War classics include:
Huckleberry Finn by Mark Twain
Narrative of the Life of Frederick Douglass by Frederick Douglass (nonfiction, but it still "counts" as literature)
Also, if you google "American slave narrative," you'll find more sources than you can possibly use, but one I'll highlight, if only because the movie made it comparatively well-known is:
12 Years a Slave by Solomon Northrup
For a controversially Southern-sympathetic source, you could look at Gone with the Wind by Margaret Mitchell
For the immediate post-Civil War era, the above google search will give you many sources too, but you might especially want to read Booker T. Washington's Up from Slavery.
For 20th century, there's way too much to pick, but some of my favorites from a few different decades are: Langston Hughes (poems and fiction)
Autobiography of Malcolm X by Malcolm X and Alex Haley (whose "Roots" you'll also want to look at)
James Baldwin (novels and nonfiction)
Toni Morrison (my favorites are Song of Solomon and Beloved)
Maya Angelou
August Wilson (he wrote 10 plays, each set during a different decade of the 20th century, so while he mainly wrote in the 80s-2000s, he has a take on any other time you want to focus on)
and you could even use the screenplays of Spike Lee (especially Do the Right Thing) as a source on late 20th century
There are major gaps even in that list, but it's a huge topic and after you do some preliminary research, your first task is most likely going to be finding your own way to narrow it down, so I hope this all at least gets you started.
Max M.
Oh, and I meant to add--if you do look at Booker T. Washington, you may want to contrast that with W. E. B. DuBois's The Souls of Black Folk. He pretty sharply disagreed with Washington. Both are nonfiction sources, though, just FYI.02/12/20