In 1936, he was a member of the British–American Himalayan Expedition that made the first ascent of Nanda Devi (7,816 m) in India, which remained the highest mountain ever climbed until 1950.
He translated material in German, French, Spanish, and Italian for use in writing the first Army manuals on mountain warfare, and developing equipment.
After receiving a master's degree from Middlebury College in 1947, Carter returned to Milton Academy, where he taught French, German and Spanish until his retirement in 1979.
Carter often used his second home in Jefferson, New Hampshire as a base camp for school trips to the White Mountains.
Due to his long work as editor of the American Alpine Journal, Carter became an important chronicler of mountaineering.