The legendary American mountaineer Lou Whittaker has died at age 95. Whittaker is known for helping lead ascents of Mount Everest, K2 and Denali, and teaching generations of climbers during his more than 250 trips up Mount Rainier. Whittaker's guide company RMI Expeditions says he died peacefully at home Sunday. Whittaker and his twin brother Jim Whittaker grew up in Seattle and began climbing in the 1940s with the Boy Scouts. Jim Whittaker in 1963 became the the first American to summit Everest. While Lou Whittaker never summitted Everest himself, in 1984, he led the expedition that included the first successful American summit from the colder north side.