re: South LA is a Catholic Heavy Area...Besides the LP. Why so?

The Northshore was overwhelmingly protestant (except for the Italians) until the NOLA exodus. As for the LP, I expect it hews more closely to what the BR demographic was until the early 20th century. The plants brought in a more urban, lower middle class, blue collar population, which means more Catholics. The LP maintained its rural, white, protestant character until it became a commuter destination for BR.