I've been to this Park several times over the last 20 years or so. Until this year it was known as the Antique Powerland. A big GM truck club from the Willamette Valley (roughly Portland down to Eugene) called the GM Haulers used to have their big annual truck shows there which I attended a few times.
I've never been to the steam-up (
http://www.antiquepowerland.com/html/steam-up.html) but need to put that on my "bucket list". Anybody interested in old machinery of all types can easily spend a whole day at the Powerland.
Unfortunately, when we were there last Sunday for the Mini-Meet, the car/motorcycle museum was not open. It looked like they were in the middle of a big expansion project, doubling the size of the building. They had more than doubled the size of the truck museum, though, since the last time I had been there. The guy behind the counter said they had just opened the expansion 7 weeks ago.