Speed Limit in Oregon on Interstates is 65. Assuming you were coming from SoCal...I-5 all the way to Portland, West on I-84, North on I-82...now you're in Washington. I don't know how those roads are in Washington, but your complaint was with Oregon.
Taking the 97 is certainly more scenic, and probably quite a bit shorter, but I doubt it's quicker. So the choice was yours- save gas and savor the beauty, or drive faster. I would have taken 97 too, but I'm not going to bitch about the speed limit. Don't blame it on the state, it was your choice.
EDIT...According to MS Streets and Trips...
Interstates- 1256 miles...18 Hours and 28 minutes.
Hwy 97- 1146 miles...18 hours and 38 minutes.
However, I've found that those time estimates are always low on the back roads and high on the interstates. I'd bet the interstates would be an hour or three faster, unless you hit Portland at rush hour. But you're going to burn a lot more gas, and the drive up I-5 through Oregon is perhaps the only part of the state that isn't beautiful. (I-84 is awesome, though.)