How does the setting in A Streetcar named Desire set the mood?

The establishment of New Orleans helps to bring to light
the fact that the South has definitely changed.  From the upbringing of both sisters at
Belle Reve to a modern metropolis like New Orleans, the South of the past has long since
passed.  In this light, the feeling of different worlds is evoked.  Blanche's discomfort
is also akin to the setting because she, too, is of a different time and world.  The
South that she knew is long gone and in its place is this new vision where she cannot be
assimilated.  The fact that the area of New Orleans in which Stella and Stanley live is
working class or poor also brings to light the difficulty of this modern vision for
someone like Blanche, who is used to the "finer things" or at least believes herself to
be worthy of these elements.  There is not much in way of happiness or contentment in
this setting, and this helps to establish Blanche's emotional climate, where there is
much unsettled and little that is constant.