This is, I believe, a Canada hawkweed (Hieracium kalmii), though it's possible that it's a not-yet-fully-bloomed Balsam groundsel (ragwort), Senecio pauperculus. Both species look a bit like dandelions.
These are moderately common in open areas on Isle Royale. This one was photographed on Scoville Point near Tobin Harbor, August 2007.