The Cascadia Cup was contested without Seattle for two seasons after the Sounders entered MLS in 2009, but Portland and Vancouver were awarded expansion teams that began play in 2011.
When did Seattle Sounders join the MLS?
The Sounders began their inaugural MLS campaign during the 2009 MLS season. Prior to the opening match, the Sounders sold all 22,000 of their season ticket packages. The 22,000 ticket holders, gave the Sounders a record for the most season ticket holders ever in MLS history.