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.
Black people were originally brought from Africa to America during the 17th, 18th and 19th centuries. They were forcibly transported across the Atlantic in slave ships (in which many died) and sold as slaves to work on sugar and cotton plantations in the Caribbean and the southern states of north America. They had no rights and were seen by their white owners as little more than animals or machines. Even after the abolition of slavery in 1865, the blacks were still almost powerless. The whites had too much to lose to allow blacks any rights. Nothing was equal: blacks had the worst of everything while whites had the best.
Such was the hatred of blacks by the whites - especially during the Great Depression of the 1930s, when money was tight for everyone - that it was common for blacks to be lynched or hanged by a mob well into the 20th century - so there was good reason for Atticus to sit outside the jail to protect Tom Robinson before his trial.
Segregation and injustice:
In the 1930s, although 50% of the population of Southern towns were black, they had no vote and could not marry whites. The policy of segregation meant that blacks had have their own schools, churches, football teams, even their own cemeteries. In the novel, Scout and Jem get into trouble with Aunt Alexandra for attending the blacks' church. The blacks file into the courthouse after the whites and have to sit up in the balcony, away from the whites.
Some whites formed vigilante groups to intimidate and even murder blacks; and right up until the 1950s it was common for black men to be accused of assaulting white women on the basis of little or no evidence. Harper Lee may have based her novel in part on a case in Scottsboro, Alabama.
The Scottsboro case:
In 1931 when Harper Lee was 5, nine young black men were accused of ****** two white women on a train. After a series of bitter trials, four of the men were sentenced to long prison sentences - even though prominent lawyers argued that the accusations were false. It was later discovered that the women were lying.
The novel is about three years in the life of the Finch family: Atticus and his son Jem and daughter Scout. Atticus is a lawyer and the central incident of the novel is when he defends a black man, Tom Robinson, against the charge of ****** a white girl. The story is told in the first person by Scout Finch, a young girl - so we see things from her point of view, and sometimes we need to reinterpret what she tells us.
Jem (aged 10) and Scout (aged 6) meet Dill (aged 7), who has come to stay with his aunt in Maycomb during the summer vacation. Dill becomes interested in 'Boo' Radley, a recluse who lives next door to the Finches and whom they have never seen. A myth has grown up locally about Boo and the children are scared of him. It is Dill's idea to make Boo come out. After that vacation, Scout starts school. Since she can already read and write, yet is told she is doing them wrongly by her inexperienced young teacher, she takes an immediate dislike to school. She gets into trouble when she tries to explain to her teacher why Walter Cunningham, from a very poor family, cannot borrow money for lunch as he will not be able to pay it back. Jem invites Walter to lunch with them.
Jem and Scout find gifts, apparently left for them, in the knothole of a tree on the edge of the Radleys' house. The next summer, Dill returns for the vacation. Jem accidentally pushes Scout in an old car tyre right into the Radleys' yard, scaring her. The three children act out spooky stories about Boo and Jem tries to deliver a note to Boo on the end of a fishing pole. Atticus stops them and tries to make them more considerate by thinking of things from another person's point of view. However, on the last day of the holidays, the three sneak onto the Radleys' property at night. Nathen, Boo's older brother, shoots at them; as they make their escape, Jem loses his trousers. When he goes back for them, he finds them neatly mended and hung over the fence, as if waiting for him.
That autumn, Scout and Jem find more presents in the knothole, (watch, spelling medal, two figures of the children carved from soap). Realise the gifts must be from Boo. When they're about to deliver a note of thanks, Nathan cements the hole up. Fire at Miss Maudie's. As Jem and Scout stand shivering outside, someone puts a blanket over Scout. Jem is convinced that Boo did it and tells Atticus about the presents and his mended trousers.
Atticus starts defence of Tom. Scout taunted about this by various kids, including her cousin Francis at Christmas gathering - he calls Atticus a '****** lover'. Jem and Scout's admiration for their father rises when he shoots a mad dog with one shot. When Mrs Dubose insults the children because of Atticus' involvement in Tom's case, Jem is so angry he beheads every camellia in her yard. So, Jem has to read to her every night for a month. When she dies, Atticus explains to the children she was a morphine addict trying to break the habit and succeeded just before death, so they should admire her courage.
While Atticus is away on business, Calpurnia - the Finches' Negro cook - takes Jem and Scout to the black church. The community there honour the children's presence out of gratitude for what Atticus is doing for Tom. Aunt Alexandra arrives to stay with the family, believing that Jem and Scout (particularly Scout) need a mother figure (their own mother died when Scout was two). There is a row when it is discovered that the children went to the black church and Aunt Alexandra forbids Scout from visiting Calpurnia's house. Dill arrives in the middle of the night, having run away from his new stepfather.
A group of local men try to persuade Atticus not to take Tom's case, but he refuses. The night before his trial, Tom is brought to Maycomb jail and Atticus sit's outside during the night. Jem, Scout and Dill sneak out to check he's OK. A gang arrives to lynch Tom, but the kids burst into the circle and Scout, recognising one of the men as Mr Cunningham, asks him politely about Walter, the tension is diffused and the mob disperses.
The trial starts. The whole town attends. The kids sit in the black balcony with the Reverend Sykes. It's clear from the testimonies of Heck Tate, Mr Bob Ewell, Mayella Ewell and Tom Robinson, that Bob and Mayella are lying. Mayella had actually led Tom on and when her father discovered her he had beaten her. Taking a break from the trial, Dill and Scout talk with Mr Raymond outside the courthouse. He lives happily with a black woman, yet he pretends to everyone that he is permanently drunk in order to escape the pressure from townspeople who could not believe that he chooses to live in such a way. Despite the overwhelming evidence that Tom is innocent, the all-white jury convicts him. All Negroes in the balcony stand as Atticus leaves the court, out of respect.
Town gossip continues after trial. Bob spits at Atticus: though he 'won', he knows he's been badly shown up by Atticus and wants revenge. The kids are anxious Bob may harm Atticus, but he calms them. Jem's been badly shaken by the trial and can't make sense of it. Alexandra holds a Missionary Society tea. Scout has to be there, wearing a dress and acting like a lady. Atticus tells them Tom's been shot dead by guards when trying to escape from prison and takes Calpurnia to help him break the news to Tom's widow.
At school, Scout learns about Hitler's treatment of Jews and is amazed that no one in Maycomb is able to connect that to the racism in the town. Bob tries to break into Judge Taylor's house and menaces Helen. Jem and Scout attend a Halloween pageant at school - about Maycomb's history, Scout's dressed as a shoulder of ham. She misses her entry on stage so decides to keep her costume on to walk home to hide embarrassment. It's a dark night and Jem realises they're being followed. They are attacked - Scout's squashed in her costume and Jem breaks his arm. Someone carries Jem home. The attacker was Bob: he's found dead, with a kitchen knife in his ribs.
While Jem is still unconscious after the attack, Scout tells her story. It dawns on her slowly that the person who rescued them - and who has stood shyly in the corner of the room throughout her explanation - is Boo Radley.
Unusually for him, Atticus takes a while to realise exactly what had happened during the attack: he initially believed that Jem had stabbed Mr Ewell (and would therefore have to face the consequences), but Heck Tate knows it was Boo who killed him. They agree to put out the story that Mr Ewell died by falling on his own knife, to protect Boo.
Scout leads Boo back home. She never sees him again. Yet, standing finally outside the window where Boo always sits, she puts herself in his shoes and understands what life must be like for him.