How long had Grant's family lived in Louisana in A Lesson Before Dying?Chapters 14-15

Grant's family has lived in Louisiana for over a century.
The story takes place in the 1940s; the family had originally been slaves on the
plantation, and have remained there even after slavery has been abolished and they have
been freed.

In Chapter 14, Grant's girlfriend, Vivian
Baptiste, comes to visit him at his place on the Pinchot plantation. Grant takes her for
a walk down to the old slave quarters, and shows her the plantation cemetery, "where
(his) ancestors had been buried for the past century." The cemetery is wooded and weedy,
and there are few actual gravestones in it. Adjoining the cemetery is the field where
Grant's "people (have) worked...ever since slavery." Grant tells Vivian that many of
those people are buried in the cemetery they had just
passed.

Despite his family's ties to the area, Grant longs
to leave Louisiana, and the South in general. He stays, however, because of Vivian, who
is technically still married to another man because her divorce is not yet final. Grant
has gotten an education thanks to his Tante Lou, and has gone to California for a short
time to live with his parents, but aside from that, he has lived in Louisiana, and the
stifling confines of the South, like his ancestors before him, all his
life.