2010 marked the 40th celebration of Earth Day, a holiday that helped spark America's modern environmental movement when it was founded on April 22, 1970, by then-Sen. Gaylord Nelson of Wisconsin. In honor of that historic day and to honor the 50th anniversary, MNN produced this quick look back at the last several decades of planetary appreciation.
1971: Amtrak is founded, even though gas costs just 33 cents a gallon.
1972: The EPA bans DDT, which was thinning bald eagles' eggshells.
1973: A Mideast oil embargo sparks a U.S. gas crisis.
1974: Congress passes the Safe Drinking Water Act, shamelessly pandering to the water-drinkers lobby.
1975: Congress sets emissions and efficiency rules for cars, leading to the introduction of catalytic converters.
1977: The U.S. adds the first plants to its endangered species list — despite their disturbing lack of cuteness.
1978: Congress bans CFCs in aerosol sprays after scientists realize they can deplete the Earth's ozone layer.
1979: A partial meltdown at Pennsylvania's Three Mile Island nuclear plant ruins an otherwise good day.
1980: Congress creates the Superfund program to clean up toxic waste sites. Those expecting "super fun" sites are quickly disappointed.
1981: Acid rain intensifies over the Northeastern United States and Canada.
1982: Dioxin contamination forces the U.S. government to buy homes in Times Beach, Missouri — not the last time it would have to buy up toxic assets.
1983: A long failure to clean up the Chesapeake Bay begins.
1984: 8.6 million acres of protected wilderness are established in 21 states. Somewhere in the distance, a coyote howls.
1985: Scientists discover a giant hole in Earth's ozone layer. During the next year's NBA All-Star Game, Spud Webb dunks through it.
1986: Congress declares the public has a right to know when toxic chemicals are released into the air, land or water. The public breathes a sigh of relief — and a little sulfur dioxide.
1987: Medical waste washes ashore in New York and New Jersey, forcing beaches to close. Efforts to rebrand the area don't work out.
1988: Congress bans ocean dumping of sewage sludge and industrial waste, ending a cherished American tradition.
1989: The Exxon Valdez spills 11 million gallons of crude oil into Alaska's Prince William Sound, one of the worst environmental disasters in U.S. history.
1990: The EPA's Toxic Release Inventory tells the public which pollutants are being released into their communities.
1991: The U.S. government begins using products made from recycled content.
1992: The U.S. Energy Department and the EPA launch the Energy Star program to label energy-efficient products.
1993: A cryptosporidium outbreak in Milwaukee sickens 400,000 people and kills more than 100, raising awareness of microbes in water supplies.
1994: The first genetically modified tomatoes hit the U.S. market.
1995: Wolves are reintroduced into Yellowstone and central Idaho. The initial awkwardness quickly fades.
1996: Public drinking-water suppliers are required to inform customers about chemicals and microbes in their water.
1997: The U.S. joins other countries in Kyoto, Japan, to negotiate a global climate-change treaty it winds up rejecting.
1998: Earth has its warmest year since record keeping began in 1880.
1999: The EPA announces new rules to improve air quality in national parks and wilderness areas. Somewhere in the distance, a coyote coughs.
2000: High temperatures and low rainfall spark the worst U.S. wildfire season in 50 years.
2001: The U.S. formally rejects the Kyoto treaty. The treaty suffers brief self-esteem issues before hooking up with Europe on the rebound.
2002: The U.S. suffers its second-worst wildfire season in 50 years.
2003: The EPA retrofits 40,000 school buses nationwide to cut back their tailpipe emissions.
2004: The EPA requires cleaner fuels and engines for farm and construction equipment.
2005: The 2005 Atlantic hurricane season produces a record number of tropical cyclones, including Hurricane Katrina, which devastates the Gulf Coast.
2006: An Inconvenient Truth is released, winning Al Gore an Oscar, a Nobel Prize and a lifetime of being criticized every time it snows.
2007: The bald eagle is removed from the endangered species list.
2008: The EPA releases a list of "eco-fugitives." Captain Planet comes out of retirement.
2009: Something happens in Copenhagen, but no one is sure what, if anything, it is.
2010: People around the world celebrate the 40th Earth Day, once again dedicating a full day to the planet's health. The Earth is touched, even though it creates days in the first place by rotating, which means "Earth Day" is a regift. But it's the thought that counts.
Sources: EPA, U.S. Energy Department, U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, NASA