Hundreds of Rhododendron albiflorum, or White Rhododendron, grow along the Grand Ridge trail at 5000'. I had only seen three individual plants previously, so it was amazing to find so many! Most were fairly close to the Deer Park trailhead.
This is Rhododendron albiflorum, or White-flowered Rhododendron, which I've only seen twice before. It was growing on the Klahane Ridge trail and conveniently labelled by park rangers.