The first Earth Day took place on April 22, 1970. Originally called the Environmental Teach-in, the movement was organized by founder Gaylord Nelson, then a U.S. Senator from Wisconsin, and his Washington, D.C.-based group of nine staff members with a $125,000 budget. They organized volunteers and events in dozens of cities and college campuses throughout the country all rallying around the importance of conservation and cleanup. 

"Earth Day 1970 achieved a rare political alignment, enlisting support from Republicans and Democrats, rich and poor, city slickers and farmers, tycoons and labor leaders. The first Earth Day led to the creation of the United States Environmental Protection Agency and the passage of the Clean Air, Clean Water, and Endangered Species Acts." – EarthDay.org

See more photos and find out how Earth Day grew into a global event on National Geographic.