Where is Calpurnia from in 'To Kill a Mockingbird'?

Calpurniia is an African American servant who can be harsh, but is really quite kind. Scout loves her very much, even if she sometimes doesn't act like it.
She is the cook for the finches. She treats Jem and Scout like they were her own kids. Calpurnia is like a motherly figure for both of them.