For many decades, Americans have felt they could do whatever they wanted with their air, land, and water. There always seemed to be plenty. It was easy to ignore environmental devastation by moving on to a new place. By 1850, for example, more than one hundred million acres of land had been cleared of trees, an area equal in size to the entire state of California. As the United States became more industrialized in the late nineteenth century, those problems became harder to ignore. More Americans became concerned about these problems, and the environmental movement was started. It continues to the present day.

The creation of national parks marked the first stirrings of environmentalism. As Americans realized the limitations of their natural resources, they wanted to preserve some untouched natural areas from development so that they would always be there for future generations of Americans to enjoy. Yosemite, in...