Monday marks Earth Day, which for more than 50 years has placed a focus on clean air and water, addressing pollution and championing conservation efforts.

U.S. Senator Gaylord Nelson led the creation of Earth Day in April 1970, seeking to hold a series of teach-ins across the country similar to those held at many college campuses in opposition to the Vietnam War.

Nelson’s work came at a time of heightening awareness about the environment that was helped along by work in the 1960s such as author Rachel Carson's book “Silent Spring.”

The success of the first Earth Day helped push the passage of two landmark U.S. environmental laws — the Clean Air Act and the Clean Water Act.

The United Nations in 2009 established International Mother Earth Day, held on the same date. A resolution establishing the observance says that “in order to achieve a just balance among the economic, social, and environmental needs of present and future generations, it is necessary to promote harmony with nature and the Earth.”

Commemoration of Earth Day includes events such as volunteer cleanups at natural areas.

U.S. President Joe Biden said in a proclamation that “building a greener, more sustainable planet” has never been more urgent, citing climate change as “the existential crisis of our time.”

“Deforestation, nature loss, toxic chemicals, and plastic pollution also continue to threaten our air, lands, and waters, endangering our health, other species, and ecosystems,” Biden said. “Our actions matter, and together we can protect our planet and our futures.”

Some information for this story came from The Associated Press.