The Organic Act creating Yellowstone National Park on March 1, 1872, not only preserved the
park’s wonders “from injury or spoilation” and retained them “in their natural condition,” but also
set the area aside as a “pleasuring-ground for the benefit and enjoyment of the people.” These
two precepts provided the foundation and influenced the development of both concession and
conservation policy in the National Park Service.Yellowstone National Park has rich human and
ecological stories that continue to unfold. People have spent time in the Yellowstone region for
more than 11,000 years. Many tribes and bands used the park as their home, hunting grounds,
and transportation routes prior to and after European American arrival. Half of the world’s
geysers and hydrothermal features are in Yellowstone, fueled by this ongoing volcanism. Lava
flows and rocks from volcanic eruptions cover most of the land area of Yellowstone. The park is
the centerpiece of the Greater Yellowstone Ecosystem, and one of the largest remaining
nearly-intact ecosystems.