Before she was known around the world for living with mountain gorillas, Dian Fossey struggled to bring attention to their dwindling numbers.

Certain that gorillas were on the verge of extinction, she adopted a brash approach to communication and conservation that ruffled many—and likely contributed to her still-unsolved murder in 1985. But this fierce dedication also helped revive the beleaguered primates. Today, thousands of tourists visit Rwanda, Uganda, and the Democratic Republic of the Congo to see them.

In 1969, the 35-year-old scientist had received three National Geographic Society grants to research the elusive gorillas, and the magazine’s editors decided to feature her findings. They quickly learned that Fossey was not afraid to offend in the gorillas’ defense.

On June 1,