Ed Viesturs

Ed Viesturs is an American high-altitude mountaineer famous for being the first American to climb all fourteen of the world's mountains that exceed 8,000 meters. Remarkably, he accomplished this extreme feat without the use of supplemental oxygen. This project, which he called "Endeavor 8000," cemented his legacy in mountaineering history.

No, Ed Viesturs climbed Mount Everest multiple times without the use of supplemental oxygen, adhering to his strict purist mountaineering philosophy. He believes that using bottled oxygen gives climbers a false sense of security and changes the nature of the ascent. He successfully summited Everest without oxygen several times throughout his career.

Viesturs completed his 16-year quest to climb all 14 eight-thousanders in 2005. His final summit was Annapurna, which is widely considered one of the most dangerous and avalanche-prone mountains in the world. His success on Annapurna finalized his "Endeavor 8000" project safely.

The project involved climbing all 14 of the independent mountains on Earth that are taller than 8,000 meters (26,247 feet), located in the Himalayan and Karakoram ranges. These include famous peaks like Mount Everest, K2, and Kangchenjunga. Completing all 14 without oxygen is considered the ultimate achievement in high-altitude mountaineering.