Aside from the KKK and other paramilitary organizations, of course (although if they acted as crime syndicates I would be very curious!).
I saw this map from 1967, and I was struck by how the crime syndicates are pretty much all centered in California, the Great Lakes, and the northeast. What about in other places, particularly the southeast? Were there regional crime syndicates, or more broadly, was there organized crime operating in a similar way as in the northeast, Great Lakes, and California (say, out of Atlanta or New Orleans)?
I just happen to be researching prohibition. Organized crime tended to be organized in large cities, and there weren't very many large cities in the south in the early parts of the 20th century. Those that were large and in the south tended to be ports.
For example, in 1920, New Orleans came in 17th place overall in city size in the US with a population of just under 400,000. It was the largest city in the south east. Atlanta came in at half that size, Dallas even lower, Jacksonville at about 100,000, and Tampa and Miami hardly registering on a list of the largest cities. Compare those to New York with almost 6,000,000 people, or Chicago with 3 million. By 1940 the situation hadn't changed too much on a relative scale.
As your map shows, there were crime families, mostly Italian/Sicilian in those few large and not so large port cities of the time. Most of them did what you would expect: Racketeering, sports betting, importing illegal goods, and so on.
The Klan itself was a horrible organization but I would hesitate to call it a crime syndicate despite perpetuating murder and arson. The Klan itself was a legal organization and primarily participated in legal activities, no matter how terrible we realize they are now. Much of the racial violence associated with the Klan was localized in the south despite the majority of its membership being elsewhere. They had a large presence in many Northern and Midwestern cities where they fought against boot-leggers quite fiercely. Prohibition was the main unifying theme across all local Klan groups. Nativism was a major cause of the Klan on the east coast and in the Midwest where there were large numbers of immigrants.
Edit: I can add more later if you want, but it's way past my bedtime. My sources are a bit thin on organized crime in the south east since it's not my focus, but it is mentioned in other books about prohibition from time to time.
Sorry I'm not answering your question, but can I ask a side question about Phenix City, Alabama and the history of the mob and organized crime? In particular "The Machine".
I linked an article that summarizes the history which or organized crime there which swiftly ended with the assassination of the States Attorney General Elect. http://malefactorsregister.com/wp/?p=815
