"Earth Day was founded in 1970 as a day of education about environmental issues, and Earth Day 2021 will occur on Thursday, April 22—the holiday's 51st anniversary. The holiday is now a global celebration that’s sometimes extended into Earth Week, a full seven days of events focused on green living. The brainchild of Senator Gaylord Nelson and inspired by the protests of the 1960s, Earth Day began as a “national teach-in on the environment” and was held on April 22 to maximize the number of students that could be reached on university campuses. By raising public awareness of pollution, Nelson hoped to bring environmental causes into the national spotlight.
By the early 1960s, Americans were becoming aware of the effects of pollution on the environment. Rachel Carson’s 1962 bestseller Silent Spring raised the specter of the dangerous effects of pesticides on the American countryside. Later in the decade, a 1969 fire on Cleveland’s Cuyahoga River shed light on the problem of chemical waste disposal. Until that time, protecting the planet’s natural resources was not part of the national political agenda, and the number of activists devoted to large-scale issues such as industrial pollution was minimal. Factories pumped pollutants into the air, lakes, and rivers with few legal consequences. Big, gas-guzzling cars were considered a sign of prosperity. Only a small portion of the American population was familiar with–let alone practiced–recycling." (History)