Elwha Campground was destroyed by flooding in the winter of 2017. The National Park Service is in the process if dismantling the campground and letting it return to natural forest land. If you are heading into the Elwha either for the day, a quick overnight or as part of the Pacific Northwest Trail the two closest campgrounds are in the backcountry; either Humes Ranch up Whiskey Bend Road or Boulder Creek up Hot Springs Road. Access to these areas is fairly difficult as no future plans for permanent bridges are in place where washouts have occurred. While the Elwha River valley is absolutely gorgeous, it is a mission to get to the upper reaches such as Glines Canyon and further upriver.
These campsites were closed indefinitely due to flood damage, but man were they beautiful when open. The entire Washington area is beautiful. Even though the campsites are currently closed there is lodging available in the Port Angeles area. You can also stay inside the park at Lake Crescent. The area is still open for hiking. I definitely recommend making a stop here during your Olympic National Park visit.