Over on this thread, commenter BusyB made a Sounders observation:

Some website, which feels icky and is sponsored by the terribly named Xfinity, corroborates:

Aug 8, 2012 - The Seattle Sounders current run of three consecutive US Open Cup titles is impressive enough on its own. In the MLS era, no other team has won back-to-back titles, let alone three in a row. The Chicago Fire currently hold the record for most US Open Cups won by an MLS team with four, a number which the Sounders can equal with a win at Livestrong Sporting Park on Wednesday night. To equal the Fire's record of dominance of the competition in only their fourth season of existence as an MLS side would be a tremendous feat, but not the most impressive. Only one other team, Stix, Baer and Fuller, has won three consecutive US Open Cups, with the last victory in their run coming in 1935 (under the name St. Louis Central Breweries.) The Sounders have a chance to accomplish something unique in the entire 98 year history of the tournament. But to do so, they'll have to best one of the emerging powers of the Eastern Conference in their own stadium.

Good luck, Sounders.