re: Older Baton Rouge residents. What lead to the decline of NBR?

Not really. While NBR has some shuddered industrial facilities and warehouses along Choctaw, there are tons of jobs in NBR. They're just by and large not being worked by people living in the neighborhood. Those middle class black families who do live in the nice parts of NBR either work at those places, teach at area schools and universities, work for the state and local government, or hold professional degree jobs.