Atticus Finch is one of the greatest fictional figures in American literature. Both in the book and in the film, Atticus stands larger-than-life, bold-and-courageous against the falsehood and injustice. He risks his life and his career (seemingly without care), as he defends a black man against charges of rape (which were based on lies, fear and ignorance).
Where Atticus Appears (and Inspiration for This Character):
Atticus first appears in Harper Lee's only novel, To Kill a Mockingbird. He is said to have been based on Lee's own father, Amasa Lee, (which puts a possible autobiographical slant to this famous novel). Amasa held a number of positions (including bookkeeper and financial manager)--he also practiced law in Monroe County, and his writing explored race-relations topics.
When he prepared for the role of Atticus Finch in the film version, Gregory Peck went to Alabama and met Lee's father. (He appears to have died in 1962, the same year the Academy-Award-winning film was released.
During the course of the novel, we discover that his wife died, though we never find out how she died. Her death has left a gaping hole in the family, which has been (at least partially) filled by their housekeeper/cook (Calpurnia, a stern disciplinarian). There is no mention of Atticus in relation to other women in the novel, which seems to suggest that he is focused on doing his job (making a difference, and pursuing justice), while he raises his children, Jem (Jeremy Atticus Finch) and Scout (Jean Louise Finch).
Atticus is a Maycomb lawyer, and he appears to be descended from an old local family. He's well-known in the community, and he appears to be well respected and liked. However, his decision to defend Tom Robinson against the false charges of rape lands him in a great deal of trouble.
The Scottsboro Case, a legal court case involving nine black accused and convicted under extremely dubious evidence, occurred in 1931--when Harper Lee was five-years-old. This case is also an inspiration for the novel.