Just as the first regular season interleague baseball game between the Baltimore Orioles and the Washington Nationals is about to begin, today's Washington Post has a feature story on the history of the rivalry between the neighbor cities. Back in the 1960s, the Senators were so bad compared to the Orioles that no one really thought much about a rivalry. The teams came from different cities, so it was nothing like the Brooklyn Dodgers or New York Giants versus the Yankees. Of course, before interleague play began, the only city with multiple MLB franchises in which such a rivalry existed was New York, where there were two teams from the same league, and where teams from both leagues often made it to the World Series. That was not the case in Chicago, Boston, Philadelphia, or St. Louis.
To mark this occasion, I have updated the Baseball cities page with new attendance data for metropolitan areas with two baseball teams.
Coincidentally, one of those cities, Los Angeles, is going ahead with plans to renovate Memorial Coliseum, hoping to win an expansion franchise. See the Los Angeles Times. The National Football League is beginning a formal process to consider various cities.