Final answer:
Earth Day was established in 1970, originating from the first Earth Day organized by US Senator Gaylord Nelson to address environmental concerns.
Explanation:
Earth Day was established in 1970 as a response to increasing environmental concerns and a call for action. The event that is said to be the reason for why Earth Day was established is the first Earth Day, created by US Senator Gaylord Nelson and organized by Denis Hayes. This day involved demonstrations, teach-ins, and community clean-ups across the United States to raise awareness about environmental issues.
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