Capital gains tax on sale of donated land

My wife sold some timberland in Louisiana. The land was donated to her by her mother; her mother received it by donation from her mother,i.e. my wife's grandmother. So my understanding is that my wife has no cost basis to use for capital gains because the donor, her mother, had no cost basis either. The land sold, 60 acres, was part of a 240 acre tract the grandmother bought from her father for
$4000.00 about 80 years ago.

Anybody have any thoughts on how to come up with some cost basis to lower capital gains tax?
My wife's sale occurred in 2014.