I've been in the Navy for 13 years. Ive been stationed in various places in the US and out. I've met and befriended literally hundreds of baseball fans. Most fans only interact with people in their local area, or on boards such as these, but I work with and hang out with fans from almost every state on a daily basis. In my experience the Cubs-Cardinals rivalry is only relevant to Cub and Cardinal fans. The San Fran-LA and Mets-Phillies rilvary is much more acknowledged by the casual fan than Cards-Cubs. At least in my circles, but they are broader than the average. As far as very recent history is concerned, I can agreee with the Mets/Phillies thing. Between the Mets back to back collapses in a heated race with Philly, and the general disdain between Philly and NY in all sports, not to mention the proximity, it's a big deal. But rivalry means a few different things, what's hot at the moment and what is always a big rivalry. Cubs/Cards is not nearly as big nationwide as many Cubs/Cards fans assume, but it's up there. That said, Mets/Phils is only relavent to Mets/Phils fans, Yanks/Red Sox is only relavent to their fans, and thee people who make money off it. Giants/Dodgers is only relavent to their fans, but that includes both east and west coast fans, since they moved and retain a fan base.