I was hiking in the White Mountains in New Hampshire, USA, and at the peak of Mount Eisenhower saw a number of large bee-like insects. They appeared to be nesting in a rock cairn, and were strikingly large---length was about 1.5" (~40mm). Weather was clear, sunny, about 65 degrees Fahrenheit. Time of year was early July. Environment was alpine tundra, a few hundred feet above the treeline. Besides the habitat and large size, they seemed like fairly typical bees (I'm saying bees because they were almost certainly hymenopterans, but didn't have the typical "narrow waist" of wasps). The abdomen was the longest part of the body. Behavior-wise, they flew in and out of the cairn, and often rested on the ground (or on backpacks, water bottles, etc). Does anyone know what species this may have been?
(I'm sorry I don't have any photos; even if species is impossible to determine without them I'd be happy for any information on possible family or genus)