The story of To Kill a Mockingbird takes place during the 1930s in a small town in Alabama in the southern United States - much like the town where the author Harper Lee herself grew up. To understand what the book is saying about racism, you need to know something of the history of race relations in the southern USA.
Nelle Harper Lee was born in Monroeville, Alabama, in 1926. Like Jem and Scout, her father was a lawyer. She studied at the University of Alabama and worked in New York. There she began work on To Kill a Mockingbird, in the mid 1950s. It was completed in 1957 and published in 1960 - just before the black civil rights movement in America really took.
The novel won the Pulitzer Prize [Pulitzer Prize: Prizes for literature, named after Joseph Pulitzer, an American newspaper publisher who was born in Hungary in 1847. ], America's top literary award, in 1961. It was adapted for the stage and was also made into a successful film. Yet Harper Lee did not write any more novels. She returned to Monroeville. Now in her 80s, she still lives there today.