The first Earth Day celebration took place on April 22, 1970. In New York City, some 250,000 people flooded Fifth Avenue.

Students at Cerritos College in Norwalk, California release a large balloon during a rally celebrating the first official Earth Day.

A close-up of a hand holding up an Earth Day button, which reads, “Save your Earth—You can’t get off.” Though urban events made the biggest splash in the press, the true impact of Earth Day came from the more than 12,000 events scattered around the country, attended by an estimated 20 million Americans.

Kurt Amuedo, a third grader at University Park Elementary in Denver, Colorado, displays poster hitting air pollution for Earth Day at school.

Students build a “world” of tin cans at Regis College in Weston, Massachusetts for Earth Day, April 21, 1970.

In Hohokus, New Jersey, Terry Seuss, 14, on Earth Day spends time cleaning up recyclable litter.

College students from University of California, Irvine observe the first official Earth Day by visiting a garbage dump in a trolley car with a poster reading “Recognize the Polluter, Recognize Ourselves.”

Children use push brooms to sweep a New York City park on Earth Day.

People looking at chart showing average emissions released into the atmosphere per mile of motor travel on the first official Earth Day.

Bicyclists wear signs on their back touting the benefits of biking over driving cars to reduce air pollution.

New Yorkers rollerskate in New York City on Earth Day, 1970.

Peter Cohen of the University of Colorado leads 260 cyclists in the “Bike Hike.” Starting the previous weekend leading up to the first Earth Day, a small unit of student cyclists left Boulder. Others joined in Fort Collins, Greeley and Colorado Springs to arrive, along with some 200 walkers, at Denver’s Currigan Hall.

Chalk art fills the streets on Earth Day on April 20, 1970 in New York, N.Y.

In NYC’s Union Square, girls plant flowers on April 22, 1970

A crowd of people gather in NYC near a large poster that shows a speech bubble from planet Earth that reads “Help!!”

Two young people attempt to share a kiss with each other while wearing gas masks during an Earth Day pollution protest march. Earth Day’s success helped spur action in Washington on behalf of the environment. Just eight months later, Congress authorized the creation of the Environmental Protection Agency (EPA), and the 1970s would see passage of a slew of environmental bills.

Through interplanetary probes, orbiting satellites and camera-wielding astronauts, NASA and partners have compiled an ever-growing image library of our own planet.Taken by the crew of Apollo 17, the last crew to set foot on the moon, this powerful image of the planet was dubbed “Blue Marble.” Taken on December 7, 1972 and released at a time of increased environmental awareness, it has been described as “one of the most iconic images, not just of our time, but of all time.”

Our moon is unique in the solar system. Other planets used gravity to capture their satellites; ours formed when a young Earth collided with a smaller planet, ultimately creating the Earth-moon system captured here, in this December 1990 image from the Galileo satellite.

Whether via satellite or from Apollo, Space Shuttle or Space Station, the last five decades have produced a growing wealth of images of our planet from orbit. This LANDSAT image shows individual reefs in the southern part of Australia’s Great Barrier Reef, the largest structure made by natural organisms on Earth.

Sarychev Volcano, in the Kuril Islands northeast of Japan, erupts on June 12, 2009, the cataclysm was captured during a fortuitously timed pass overhead by the International Space Station (ISS).

Super Typhoon Noru photographed by ISS astronaut Randy Bresnick above the Northwestern Pacific Ocean on August 1, 2017. “You can almost sense its power from 250 miles above,” said Bresnick at the time.

Blue meltwater streams and ponds dot the surface of the Greenland ice sheet in this 2016 satellite image. Although this is a natural phenomenon every spring and summer, it is happening earlier, faster and more extensively as the Arctic warms.

In the past, large icebergs would break from Antarctica’s Pine Island Glacier every four to six years. Calving then began to occur almost annually. This calving, in October 2018, produced an iceberg dubbed B-46 that, until it began to fracture, was 87 square miles in area.

For centuries, expedition after expedition failed to navigate the fabled Northwest Passage through Canada’s Arctic Archipelago, thwarted by impenetrable ice. A warming climate saw conditions gradually change, and in this 2016 image the former graveyard of explorers is almost completely open and navigable by cruise ships.

From space, it is possible to see not only the impacts of a changing climate, but also the fossil fuel use that is responsible for them. In the bottom right of this astronaut photograph is Kuwait City; at the top is the Iraqi town of Basra and its suburb Zubair. The lines of blotches just left of center are gas flares from the Zubair oil fields, among the brightest such flares observed from space.

The mass of light in the bottom right is South Korea; across the top left of the picture are the lights of southeastern China. The dark space between them is North Korea, the faint glow of Pyongyang the only illumination from the hermit kingdom.

On September 11, 2001, NASA astronaut Frank Culbertson was on board the International Space Station, the only American on the crew. As the ISS flew over the New York City area, he trained a camera on the scene below and documented this plume of smoke extending across Lower Manhattan from the World Trade Center.

Wildfires that burned through large swaths of Australia in late 2019 and early 2020 is here captured by this image from the Operational Land Imager (OLI) on Landsat 8 of burned land and thick smoke covering Kangaroo Island.

From a distance of 898 million miles, Earth appears as a tiny speck beneath Saturn’s rings in this image from the Cassini spacecraft.

As it headed out of the solar system forever, Voyager 1 sent back one last shot of its home world, a pale blue dot in the vastness of space. This version, released in 2020, uses modern image-enhancing software and techniques to brighten the iconic image.

Compiled from a series of images taken by the Lunar Reconnaissance Orbiter (LRO) on October 12, 2015, this image evokes the first “Earthrise” photograph, taken by William Anders from on board Apollo 8 in 1968. Noted Jeffrey Kluger in TIME magazine upon the image’s release: “The moon has not felt the press of human boots for 43 years, and it could be many more years before it does again. But the view from the world we visited and left remains spellbinding.”