I don'I don't know. The midwest is very fragmented. Lots of teams to chose from. Since they're the most consistently successful they have more than their fair share. What I don't know is if St. Louis is a town where people grow up and stay in or come back to or if it's a place where people grow up, go to school and then move to one of the coasts. If that's the case, they'll have a pretty good fanbase nationally. Locally, it's as strong as any in baseball.
St. Louis is definitely a city where people tend to stay. When you just meet someone the popular saying in st. Louis is, where did you go to high school. That's just how we identify what part of St. Louis you're from. Once you get out of the city the suburbs are actually really nice. We also draw from quite a few states, Iowa, southern Illinois, Kentucky, Tennessee, and Arkansas. The only team i can think about that is around these states are the braves. Unlike the east coast, the cardinals actually have a pretty big following on the west coast. Didn't see many Cards fans at the games in Washington. But it is hard with the Nationals red and red towels. Which actually looked neat on TV, wish the cards would do red towels.