The Gorge does have train tracks on both the OR and the WA side, but none of them go right through the campgrounds!!! Tracks are close to some sites, and not so close in some campgrounds.
Look at Plymouth Park (Corps of Engineers), Crow Butte Park, Maryhill State Park, all on the WA side. On the OR side are Boardman City Park, LePage COE Park, Memaloose State Park, Viento State Park, Marine Park Campground in Cascade Locks. All are listed from east to west and are personal picks, and not private campgrounds. Most if not all have reviews you can find.
Where in Minnysoda are you leaving from??