According to the Saint Louis Post Dispatch: http://www.stltoday.com/stltoday/news/stories.nsf/stlouiscitycounty/story/2239371C410EE4698625741B001DB75A?OpenDocument
Regional barbecue styles
Barbecue is a highly regionalized fare, with major, and passionately debated, differences. Barbecue is generally distinguished by a long, low exposure to heat. From there, the differences in style depend on meat, wood, spice and sauce.
— Texas style: Beef brisket, with tomato-based sauce put on after cooking.
— Kansas City: Pork spare ribs or beef brisket, typically distinguished by a thick tomato-based sauce.
— Memphis: Baby back pork ribs, with a dry spice rub. A spicy-sweet tomato-based sauce is usually used for dipping.
— St. Louis: Pork spare ribs or pork steak, distinguished by a sweet barbecue sauce.
— North Carolina: In the eastern part of the state, it is served with spiced vinegar; in the western part, with a vinegar sauce with ketchup. In both parts, the traditional meat is pork shoulder.
— South Carolina: In the northern part of the state, it is served with mustard sauce; in the southern, often served with a vinegar sauce with ketchup and brown sugar.
Another thing. Mike gave us a tour of the kitchen at Pappy's and said he used fruitwood (apple and cherry). He said folks in St. Louis preferred it to the stronger flavor of hickory used down South. I was born and raised down South, so I prefer the hickory.