I've not dug in Louisiana, but we have some spots here that had or still have old plantation homes and you can pretty much dig around any of the plowed fields and find stuff because they were 1,000 acre plus cotton fields. The hard part is determining who to ask, but that is what I would be trying to seek out. Find some fields in the old parts of the country and door knock. Nothing else go to a yard sell where there are older folks and ask them some places to go or people who would possibly allow you to dig on their property. I learned that you have to ask specific questions such as "do you know if there are any old schools, 1930s or older?" or people will head scratch more than remember.