It was first performed in the late 1940's so it is considered very modern for American Theatre but this is less than 100 years after the American Civil war.
The American Civil war was a war about slavery between the north and south
The late 1940's was before the basic integration of people of colour into society and before things like Selma and Martin Luther King
Tennessee Williams plays into a tradition of southern literature, inspired by authors like William Faulkner and Eudora Welty. This is a very important part of the localization of the culture of the play.
In the 1940’s, the South, particularly New Orleans, it was viewed as anothercountry compared to NewYork or California.