Mick says the same applies in Oregon with the trailer speed. It just says "truck speed", so I am not so sure. I still go slightly above our posted car speed, because we like to get places a little quicker right now. One day we might slow down a bit. California has the same rule as OR and WA, and you can get away with faster, but dad was pulled over outside Redding years ago on our way back from waterskiing at Shasta. Cop was none too pleased at the trailer sway and dad's argument. Dad walked away with a fine/ticket and a bad attitude for the rest of the drive. Good times!
I sure love Montana, Idaho, Wyoming...pretty much anywhere in the prairies where we can open it up a bit. I feel pretty comfortable at 75, but don't get to do it until we get over the passes. Oregon is the slowest state on the left coast, but no idea why. I remember our past governor holding a higher speed limit ransom a few years back. The deal never went through and the speeds have stayed the same. He claimed too many people would die. I don't know about that with an extra 5 mph.