When did the south become a fully segregated society?

After the southern Populist were defeated.  
The South turned out to be completely isolated by law amid the 1890s, after the thrashing of the Populists and their endeavor to advance biracial, multiparty governmental issues. The Redeemers did not establish isolation or disfranchisement even after the Republicans in the North deserted southern blacks. After the War, the Reconstruction approaches of Republicans had made separation and isolation difficult until this day.

River valleys were good places for hunting and fishing.