The first federal environmental act was the establishment of Yellowstone National Park in March 1872 in the territories of Montana and Wyoming. Instead of promoting the land for development, Congress and President Ulysses S. Grant declared that it should be preserved "as a public park or pleasuring ground for the benefit and enjoyment of the people." As the first such preserve in the world, Yellowstone inaugurated an international national park movement that currently includes some 1,200 parks or preserves in 100 countries, including 391 in the United States.
The Scottish naturalist John Muir became an early advocate for preservation after his travels and scientific work convinced him that some natural areas need protection from human exploitation. Muir founded the Sierra Club in 1892 to that end and urged President Theodore Roosevelt to join the cause. Roosevelt, himself known as an ardent outdoorsman, eventually dedicated more than 150 million acres to national parks and forests, and founded the US. Forest Service, which manages forests for water and timber resources while protecting them for wildlife and recreation. The first chief of the Forest Service, Gifford Pinchot, promoted a "wise use" strategy of wilderness management that proposed, in contrast to Muir, that nature could be safely commercialized.
Another early American environmentalist, Aldo Leopold, called for a "land ethic" that recognized the value of the natural world as beyond financial. In 1924, due to Leopold's efforts as a Forest Service employee, the Gila National Forest in New Mexico became the world's first designated wilderness. This designation allows travel only by foot or horseback and bans any commercial activity except grazing in order to protect the usefulness of the wilderness for cleaning air and reducing climate change, as well as providing clean water, wildlife habitat, and natural recreational experiences.
Interest in environmental issues escalated again in the late 20th century due to the increasingly visible effects of human behavior on the environment. "Going green" is now an international movement addressing land and water conservation, air and water pollution, solid waste disposal, global warming, and biodiversity. (‘The New York Times ‘Smarter by Sunday – 52 Weekends of Essential Knowledge for the Curious Mind’)