In Harper Lee's To Kill a Mockingbird, what are some connections to important themes/issues in US history? How does this book help you better understand US history? What is missing? (cited quotes would be greatly appreciated)

The most significant event in American history that connects to Harper Lee's To Kill a Mockingbird is the trial of the Scottsboro boys in 1931. To summarize the events around the trial, in 1931, nine innocent black young men, ranging in age from 13 to 19, were accused of raping two white women on a train in Alabama. The court found them guilty of the crime, even though one of the supposed victims took back her accusation, and all nine boys were sentenced to death. After six years in prison, the charges against the boys were dropped, and eventually, they were all freed, but their lives were never the same. This event may have inspired the trial of Tom Robinson, as many of its themes are echoed in the novel.
By 1960, when To Kill a Mockingbird was published, race relations in America were tense and Martin Luther King Jr. had been working for several years with others to promote civil rights for all, including the right to vote for black American citizens. The theme of racial tension is one that Harper Lee explores in detail in the novel, making relevant connections between her fiction and the true events in American history happening around the time of publication.