There are few 50-milers out there as epic as the Washington coast. A local Boy Scout group I've been involved with over the years just got back from that trip. They started at Oil City and ending at Shi Shi beach, near the northern most point of the Olympic Peninsula. It was all just a walk on the beach, though. There's some seriously rugged terrain in between those two points, including a lot of bouldering and areas so steep they require ropes to ascend. Some parts of the trail have to be timed with low tides, making it very important to keep pace on those days. Overall the trip went very well. They all arrived back home tired and a bit blistered.
I've lead a Scout group on a 50-miler backpacking trip and it was amazing. It's one of the best experiences a young man can have in the outdoors. There are so many skills and experiences that can be learned on a long distance backpacking trip. It's an experience they will never forget and will always be proud that they accomplished.
I'll let the photos tell the rest of the story.