I-90 or Snoqualmie Pass is the largest and only divided East-West arterial in Washington State. It has the lowest elevation of any of the passes and thus tends to provide the most reliable route into the mountains and across the state. It carries an average of 29,000 vehicles PER DAY. As you can imagine, this means that although it offers some wonderful outdoor experiences, being the backyard for the greater Seattle area you will be sharing tose experiences with others. The truth is, I tend to avoid I-90 because of the crowds. It has only been in the last year as I have started to hike with others that I have begun to become familiar with where most of the Seattle area goes to hike first.
As always, practice Leave No Trace. Pretty please.