Interesting, That's where I graduated from high school many years ago. I don't know if they have sites all year round but you might touch base with the Skamania County Fair Grounds (how to do that I don't know). I know they have RV slots during special events or used to. Closest RV park that I remember with hookups is across the river in Cascade Locks, a KOA if memory serves me correctly. The ones listed in RV park reviews were not there when I lived there and I haven't visited there for several years. The couple of RV parks that were there several years ago were not really RV parks but home mobile parks that would rent a vacant space. Vancouver, Portland, Bingen and Hood River are not all that far, maybe and hour drive and I'd guess you might have a better selection in those areas.
There is a state park at Beacon Rock a few miles west of Stevenson, limited on size and I don't remember if they have hook ups. Good luck.
Bob, Sandi & Marmaduke the Big Pug
SW OREGON 2004 Journey 39K, 330 Cat
If towing: a 2006 Mini Cooper or 1995 Wrangler