This isn't a well-known stat but the Washington Nationals are on the verge of breaking it.

That franchise (Expos/Nats) has played 48 seasons, and spring training '17 will be its 49th. The record for the longest it's taken a franchise to get to the World Series is 50 seasons: the Senators/Rangers, which were born in 1961 and didn't win a pennant until 2010. So if the Nats don't go next year, they'll have tied the record. And if they don't go in 2018? New record-holder!

Of course, my Mariners aren't far behind. And right now we're the only two teams still in the running:

* I include 1904 and 1994, years in which we didn't have a World Series. Just easier that way. 

** And counting

Interesting to note that, of the original 16 teams, the two teams that took the longest to make it to the Series were both St. Louis franchises: the Cardinals in 1926, and the hapless Browns in '44. St. Louis was also the southernmost city during this time, so not sure if the heat got to them over the course of long seasons or if it was just general incompetence. Since the Cards bounced back in such a big way under Branch Rickey, and have since become by most measures the winningest team in the National League, I assume the latter.

Also interesting to note: the Yankees, which became the winningest franchise in sports history, took 4th-longest to finally win a pennant. 

Here's the chart sorted by the last column: year of first World Series:

Again, interesting to note that gap between 1907 and 1914 when there was no new blood in the Series. By this point, eight teams had gone, and the next six years they kept recycling in and out: Cubs, Tigers, Pirates, Athletics, Giants, Red Sox. Then the Braves snuck in. 

Oh, and the record for the longest time it's taken a franchise to win a World Series? That's still 78 years and it belongs to the Philadelphia Phillies (1903 to 1980). Nine teams still have a shot at that dubious record but no one is within 20 years. Look for an update in 18 or so years.