Harper Lee's novel is very effective in its setting as it is very detailed and creates a definite "reality", using such techniques as costumes, language and the predjudice and beliefs of the time.
In particular you get a sense of the time it is set in by the popular belief that Negroes are inferior. The strict code of the times setting out how you are to behave is evident in relationships(family,between adults and children), education(concentrating more on behaviour than the actual learning), and all throughout the community(the church, shops, court house etc.) The Morals and actions of then are certainly very different from those of today.
In order to create a sense of time and place in the novel, Harper Lee makes extensive use of colloquialisms. That is, she displays the characters of the people of the book through the way they speak. In order to create the setting of the book she has made the characters use southern dialect. This sets the book in southern America. The prejudices and the ideas in the book place it in the 1930's.
The clothes that Harper Lee describes in the book also help to give the reader the impression of southern America during the financial depression of the 1930's.
All in all we believe that Harper Lee effectively creates a sense of time and place in the novel,to kill a mockingbird.