What were Ansel Adams key achievements?

Context: Ansel Easton Adams was an American landscape photographer and environmentalist known for his black-and-white images of the American West. He helped found Group f/64, an association of photographers advocating "pure" photography which favored sharp focus and the use of the full tonal range of a photograph. He and Fred Archer developed a system of image-making called the Zone System, a method of achieving a desired final print through a technical understanding of how the tonal range of an image is the result of choices made in exposure, negative development, and printing.
Adams was a life-long advocate for environmental conservation, and his photographic practice was deeply entwined with this advocacy. At age 12, he was given his first camera during his first visit to Yosemite National Park. He developed his early photographic work as a member of the Sierra Club. He was later contracted with the United States Department of the Interior to make photographs of national parks. For his work and his persistent advocacy, which helped expand the National Park system, he was awarded the Presidential Medal of Freedom in 1980.

Answer: Ansel Adams was a famous landscape photographer and environmentalist. His photography focused on black-and-white photos of the American West. He garnered critical acclaim for his technical understanding of imaging along with being a vocal advocate for environmental conservation. He won the Presidential Medal of Freedom for helping to expand the National Park System through his photography.