We recently stayed at the Sappy Hollow Campground at Mt. Index Sanctuary, and had a great stay! Travis is a wonderful host, was very welcoming, meeting us at the private gated community, showing us around the campground, and answering our questions.
The few campsites are clean, large and private, with a picnic table, fire pit, and nearby sink and porta potties. The campground is spacious, with open areas ideal for families with children, and it's a short walk to the scenic Skykomish River. It's conveniently located in Index, just a few miles off of Highway 2, and is close to many nearby popular hiking trails, our main reason for staying in the area! I highly recommend it!