Jim, The town is at ~8,000', but I believe the Mammoth Mountain Inn (at the main ski area - end of Hwy 203 in the winter)is at ~9,000'. That is the highest place I know of that is open/reachable in the winter.
Mt. Whitney hut: very comfortable and private lodging at 14,505, though it takes a bit of uphill walking to get there and there is no concierge service