Seaquest State Park

I used this campground as a convenient place to stay when exploring the west side of Mt St Helens. The campground was fine but nothing to get excited about. It was a long walk to the bathroom from my site. Luckily my site did seem a bit private because I didnt have immediate neighbors. Also the sites are mostly nestled into the greenery so at least you will have some visual screening from neighbors.
I could hear quite a bit of road noise but it didn't really bother me at night when sleeping.
Many of the sites are not level so keep that in mind.
I wouldnt go out of my way to visit this campground but there were lovely places nearby. The Mt St Helens visitor center/museum? ($5 fee) is a short walk across the road and there is a mile long trail around a wetland that is nice.
I very much enjoyed visiting the Johnson Observatory up on Mt St Helens (bring your National Parks pass) and the beautiful drive up the mountain. It takes about an hour to get there from the campsite. I stopped a few times for photos and walks. There is a short lake trail on the way (Clear Lake?) that is very nice. The drive was extremely foggy in the morning, so use caution.
It's a quick drive from the campground down to Castle Rock where I had cell service. I didnt have any at the campground or up the mountain.

We stayed in the RV loop area which is really a bit of a step up from a parking lot. A couple of the spots had decent shade but most were open and close to the trailer next to you. The site had all of the hookups which was very nice when our grey water tank for full midway through the trip. Park Location was not that bad though it was an hr at least to get to Mt St Helens. Also, there was supposed to be lake access but we had a hard time finding it, maybe it was just us. The other area of the campground had nicer spots but most might have been tight for a 27’ trailer. We would stay here again in the non-T section but if going to the area again we’d probably look for something closer to the mountain and other lakes. Either way, we still had a nice stay here. The hosts were really nice.

We mistakenly parked in the RV Loop the first night (T13 vs 13) and fortunately, the folks who had reserved that spot weren't arriving until the next day. We got it all straightened out the next morning, and our spot in the main campground was actually much prettier. We were glad we weren't in a larger rig, though, because the roads through the main campground are VERY tight, and we watched, cringing, as some big rigs made their way through the trees.

Although this is the nearest state park to Mount St. Helens, it is still 50 miles to the national park itself, and if you don't have a toad, it can be a bit inconvenient to travel between the two places. You will also need the appropriate parks pass for the national park or pay a daily fee to park in the lot.

Seaquest itself has a nice visitors center, gift shop, and a coffee/shave ice stand outside that operates seasonally and on weekends. There is a nice trail, approximately one mile, around Silver Lake through the marshlands. There is abundant wildlife in the marshes including Great Blue Herons, all variety of waterfowl, fish, frogs, etc. You can see the mountain in the distance from the trail.

In the park itself, there are trails through the woods and a partial forest service road connection. We used them for some trail running and encountered almost no other people while out and about in the woods.

Negatives: distance from the mountain, no doggie poo bags available, the swing set in the playground nearest to us desperately needed to be oiled!

Positives: pretty wooded trails, nice trail around the lake, good Visitors Center

We camped in the "RV Loop" , which was like a parking lot with only a strip of grass/gravel separating you from your neighbor. We found it to be crowded and noisy, even at the end of August, on a Monday. We would recommend checking out the North or South loop pull through sites, which offer more privacy. The park is beautiful and wooded and we had a hiking trail right next to our site. The campground is also conveniently located right across the street from the Mt. St. Helens Visitor center and Johnstons Ridge Observatory was about an hour away. We were charged a Washington State recreation fee of $5 and a reservation fee of $8 for booking online. Cell coverage was really spotty here, we could get 1 bar of LTE if we stood in certain spots, but otherwise it was non existent.