It's July 1 and for the first time since 1977, both the Cubs and White Sox are leading their divisions this late into the season. In fact, it could be argued that both should easily win their respective divisions.
With that in mind, I did a little research into how often teams from the same city made the postseason (there were, until team movements began in the early 1950's, four cities with two teams: Chicago, Philadelphia, Boston and St. Louis, and one: New York, with three). During the pre-expansion era, from 1903 to 1968, when only one team from each league made the World Series, it happened fifteen times:
1906: Chicago Cubs/Chicago White Sox
1921-23-36-37-38-51: New York Giants/New York Yankees
1944: St. Louis Cardinals/St. Louis Browns
1941-47-49-52-53-56-57: Brooklyn Dodgers/New York Yankees
Beginning in 1969 two teams from each league qualified; in 1995, that was expanded to four. You'd think this would make a same-city postseason more likely (and there are still four metropolitan areas with two teams: New York, Chicago, the Los Angeles megalopolis, and the Bay Area of San Francisco and Oakland) -- but it's actually become less of an occasion, only eight times in nearly 40 years:
1971: Oakland A's and San Francisco Giants both lost in League Championship series
1989: Oakland A's defeated San Francisco Giants in World Series
1999: NY Yankees won World Series; NY Mets lost in Division Series
2000: NY Yankees defeated NY Mets in World Series
2002: Oakland A's lost in Division Series. San Francisco Giants lost in World Series
2003: Oakland A's and SF Giants both lost in Division Series
2004: Anaheim Angels and LA Dodgers both lost in Division Series
2006: NY Yankees and NY Mets both lost in Division Series
That's it -- and the Cubs and White Sox, despite having nine combined playoff appearances between them since 1983 (Sox: 1983, 1993, 2000, 2005; Cubs, 1984, 1989, 1998, 2003, 2007), haven't joined the party in the same year yet. But now, there's a hint that they just might. The two sweeps the past two weekends, one giving joy on each side of town, was just a tiny taste of what might happen come this October. It's no lock or guarantee, but for the first time in a century, fall in Chicago might be painted in baseball colors.