The best rivalry, or “Derby,” if you prefer (I prefer not), continues this Sunday when the Seattle Sounders travel to Portland to take on the Timbers (ESPN, 4 p.m. ET); the two Cascadia clubs tied 1-1 in their first MLS meeting back in May. Why is this Pacific Northwest fixture the most intense in the nation? One word: history. Here’s a quick look at that history, albeit from a decidedly Portlandia perspective.