April 22, 1970, the date of the first Earth Day celebration in the United States, is often cited as the start of the modern environmental movement. On that day, 20 million Americans filled parks and took to the streets in a nationwide teach-in and protest about critical environmental issues facing the United States and the world.
Many other people associate the beginning of the environmental movement with the 1962 publication of Rachel Carson's groundbreaking book, Silent Spring, which spelled out the dangers of the pesticide DDT. The book awakened many people in the United States and elsewhere to the potential environmental and health hazards of using powerful chemicals in agriculture and led to a ban on DDT.
Still others might point to May 28, 1892 as the day when the U.S. environmental movement began. That is the date of the first meeting of the Sierra Club, which was founded by noted preservationist John Muir and is generally acknowledged as the first environmental group in the United States. Muir and other early members of the Sierra Club were largely responsible for preserving the Yosemite Valley in California and persuading the federal government to establish Yosemite National Park.
No matter what first sparked the U.S. environmental movement or when it actually began, it's safe to say that environmentalism has become a powerful force in American culture and politics. Ongoing efforts to understand more clearly how we can use natural resources without depleting them, and enjoy natural beauty without destroying it, is inspiring many of us to take a more sustainable approach to the way we live and to tread a little more lightly on the planet.