For nearly 40 years I was on the road just about every week. I racked up 49 states, coast to coast in Canada and eight countries in Europe. Always with at least one radio (in addition to the radio in my company or rental car). When I began my career, WGN was actually a relatively easy nighttime catch in most West Coast locations. Then in the mid 70s, KDWN in Las Vegas came on with 10kw at night and most of its night signal beamed east. You could sometimes hear WGN underneath KDWN sometimes (I'd listen for Eddie Schwartz' voice to cut through). But in the 1980s, even that became more difficult when KDWN went to 50kw fulltime.
As for Seattle, WGN has always been tough duty due to local 50kw KIRO on 710. I've never heard WGN in Seattle, although I have heard them in Vancouver and Portland. But not recently. There's also a 710 in Los Angeles, KSPN, But they drop to 10kw at night and are much easier to null than KIRO.