Why did Harper Lee choose her own setting?

Harper Lee wrote To Kill a Mockingbird during a very tense time racially in her home state of Alabama. The South was still segregated, forcing blacks to use separate facilities apart from those used by whites, in almost every aspect of society. The Civil Rights Movement began to pick up steam when Rosa Parks refused to give up her seat on a bus in Montgomery, Alabama, in 1955. Following her bold defiance, Marin Luther King, Jr., became the leader of the movement, and the issue began to gain serious national attention. Clearly, a prime subject of To Kill a Mockingbird, namely the injustice of racism and inequality in the American South, was highly relevant at the time of its publication.

Interestingly, Harper Lee decided to set the novel in the Depression era of the 1930s. The main character, Scout, is based on Lee's own childhood, and Dill is most likely based on her childhood friend and neighbor, Truman Capote. By placing her novel in the 1930s, Lee provided her readers with a historical background for current events of the time, and in doing so she exposed the deeply rooted history of the civil rights struggle in the South.