EARTH DAY is an annual observance, held on April 22, to increase public awareness of environmental problems. Each year on Earth Day, millions of people throughout the world gather to clean up litter, to protest threats to the environment, and to celebrate progress in reducing pollution.

Earth Day began in the United States. In 1969, U.S. Senator Gaylord A. Nelson suggested that a day of environmental education be held on college campuses. The following year, the lawyer and environmentalist Denis Hayes, then a recent graduate of Stanford University, led hundreds of students in planning and organizing the first Earth Day. About 20 million people participated in the original observance on April 22, 1970.

The first Earth Day in 1970 helped alert people to the dangers of pollution and stimulated a new environmental movement. That same year, Congress created the Environmental protection Agency also passed the Clean Air Act of 1970.