Based on the work of geophysicists Bruce Heezen and Marie Tharp, this 1968 map of the ocean floor helped bring the concept of plate tectonics to a wide audience. Tharp began plotting the depths in 1950 from soundings taken by ships in the Atlantic, but, as a woman, wasn’t allowed on the ships herself. In 1978 she was awarded the Society’s Hubbard Medal for her pioneering research.

From an article covering 100 Years of National Geographic Maps.