What is the significance of the two houses in Emily Bronte's Wuthering Heights?

The houses to which you refer are Wuthering Heights, home
of the Earnshaw family, and Thrushcross Grange, home of the Linton family.   Both houses
are family estates located in the Yorkshire moors of England.  This areas was an open,
marshy area with few people living close together.

These
houses serve as a contrast to each other and represent the way of life of the
inhabitants.  As the novel opens, the reader sees Wuthering Heights through the eyes of
Lockwook; it is a dark, creepy, angry and unhappy place.  This reflects the figuratively
dark natures of its inhabitants, Heathcliff, Catherine Linton and Hareton.  From the
death of Mr. Earnshaw, the Heights has been filled with death, revenge, and
anger.

Thrushcross Grange, however, is not filled with such
hate.  It represents happiness and beauty.  The lights are bright; the house is filled
with music, and the family entertains frequently.The Linton family is introduced as
mirthful and genuine.  In fact, Catherine is drawn to it because of this, which sparks
the animosities between the two families.