Archaeological evidence has shown that humans have inhabited the parks for 10,000 years. When Europeans began to arrive they encountered three main Indian groups: the Western Monache, the Yokuts, and the Tubatulabal. As was common in other parts of the country when Europeans made contact, the Indians in were exposed to diseases and their population decreased significantly. So by the 1800s, when European settlers began to arrive in large numbers, much of the native population had died.
Efforts to save the ancient trees in both parks from lumber companies began in the second half of the 1800s. One settler who led the way was settler Hale Tharp, who made a home inside of fallen sequoia tree in the Giant Forest grove (it is still intact today and visitors can peek inside). Tharp met famous naturalist John Muir, who stayed with Tharp in the cabin. Thanks to theirs and many others' efforts, both parks were established to protect these ancient forests.