Couple things to add...
Pretty good reviews here but I'd add a couple things. There are two campgrounds on either side of the park. One has at least two loops of tent sites (no hookups) with water, flush toilets and showers. This site is below the dam that creates Lake Easton. There's a nice river walk tail along the Yakima River but no lake view. There is also a very busy rail line immediately on the other side of the river. Many campers have mentioned the freeway traffic noise in this park but I was bothered much more by the rail noise. There's a small switching yard only about a mile away from the site in the town of Easton. The horns and start up of these huge trains at 3 AM sound like the end of the world!
The site on the opposite side of the park (NW) has one loop of full hookups, asphalt parking pads for RV's and is on a bluff overlooking the lake. The views will take your breath away! While you are well away from the rail noise, this campground is much closer to the freeway. Depending of the time of day (and the number of motorcycles going by) it can be a little difficult to hear conversation.
Both spots are very pretty but you have to "pick your poison" when it comes to the noise.