Earth Day was established in 1970 at a time when social activism was at a high. U.S. senator Gaylord Nelson (D-Wis.), recognized a growing environmental concern that had barely been addressed by the legislature. In setting aside April 22 to recognize human impact on the environment, Nelson hoped first and foremost to raise the awareness of politicians.

Nelson certainly achieved his goal. More than 20 million Americans participated in this first Earth Day celebration, causing voter-hungry politicians to take notice. The overwhelming response helped generate a new political focus on the environment. As that focus has become increasingly global, more people than ever are celebrating Earth Day around the world.