For the world, it led to the 1992 Earth Summit in Rio de Janeiro, the largest gathering of heads of state in history, and to international treaties protecting the atmosphere and the oceans and banning the export of toxic waste to poor nations.
And yet, as the 25th Earth Day was celebrated Saturday, environmental policy is facing one of its most severe challenges as a Republican-dominated Congress moves to curb a host of environmental laws.
"This is the greatest threat to the environment . . . the greatest challenge since that first Earth Day," said Fred Krupp, executive director of the Environmental Defense Fund.
While some of the problem can be attributed to shifting political and economic winds, at least part of the current backlash, officials and environmentalists said, comes from the environmental movement's own successes and failures.
"We've done the easy things, and we've been successful," said Interior Secretary Bruce Babbitt in an interview last week. "That may have led to some complacency."
The first targets of environmental laws were big industry and big polluters - oil and chemical companies, automobile manufacturers and power plants.
"It was easy to focus on a few big corporations," said Stuart Hart, director of the University of Michigan Corporate Environmental Management Program.
The results were striking.
* Between 1970 and 1993, emissions of the basic air pollutants, such as carbon monoxide, soot and organic chemicals, were cut nearly 60 percent to about 174 million tons annually.
* Today, nearly two-thirds of all the nation's lakes, rivers and streams meet clean water standards, up from 36 percent in 1972, according to the federal Environmental Protection Agency.
* During the last two decades, 90 million acres of federal land have been added to the wilderness system, and 500 new wildlife refuges have been established.
* In just five years - 1988 to 1993 - annual emissions of toxic chemicals
from industrial plants were reduced by 43 percent to 1.6 million tons, the EPA said.
These accomplishments were spurred primarily by a barrage of federal environmental laws. Between 1970 and 1990, Congress approved 28 environmental bills, including legislation to control pesticides, to manage solid and hazardous waste, to protect endangered species, to preserve wilderness, and to ban ocean dumping.
Most of these laws required "command and control" regulations. They not only set cleanup standards, but dictated the type of technology that had to be used and required detailed supervision by regulators.
As a result of command and control rules, spending on environmental protection rose three times faster than the gross national product during the last 25 years. More than $35 billion was spent on sewage treatment plants alone.
In the 1980s, a Democratic Congress wrote tighter and tighter environmental laws in large part to prod the Republican administration of Ronald Reagan, which was reluctant to enforce the existing regulations.
What worked in the past, critics say, will not necessarily work in 2000. And some of the gains are already unraveling as population, consumption and development continue to grow.
One emerging problem has been that regulation has continued to move to lower levels of business and even into the home. The EPA, for example, already has issued new specifications for the manufacturer of gasoline-driven lawn mowers and is considering new rules for the local dry cleaner.
"It's the old line from the Pogo cartoon: 'We have met the enemy and they are us,' " said Isadore Rosenthal, a senior fellow at the Wharton School's Risk and Decision Center.
"What we are dealing with now are broad sources of pollution, (storm) runoff, ambient air quality," Rosenthal said. "You can no longer point a finger at a plant."
Of course, there are still plants that are polluting, but they are rarely owned by large firms. "It's the small- and medium-sized companies that are the ones that are up against it now," said Hart of the University of Michigan.
For regulators, trying to use command and control rules in this setting is a nightmare. Instead of trying to monitor a handful of large installations, they find themselves trying to ride herd on thousands of small businesses. This has created the makings of a bureaucratic morass.
There has also been a resistance among citizens to new proposed controls on their lifestyles - tougher auto inspections or limitations on commuting, for instance.
These, combined with contentions by unsympathetic economists that environmental regulations cost jobs, began to create a backlash against some environmental laws.
These feelings were slowly boiling when the Republicans took control of Congress this year and announced that, as part of their Contract With America, they were going to reform federal regulations and get government off people's backs.
"People are angry in general with government . . . and some environmental laws after 25 years could be written better, made simpler," EDF's Krupp said. ''But let's not confuse what is happening now in Congress with revising these laws. What they are doing is trying to gut all environmental legislation in one fell swoop."
Not so, counter the Republican legislators. "What we have tried to do is maintain the standards but give industry and municipalities more flexibility in meeting them," said Jeff Nelligan, a spokesman for Rep. Bud Shuster (R., Pa.).
Shuster, who chairs the House Transportation and Infrastructure Committee, has sponsored a controversial revision of the Clean Water Act that has been passed by a House committee. One of its aspects that has drawn the most fire was Shuster's use of amendments provided by industry panels.
"What you've got is timber and chemical lobbyists sitting up there on (Capitol) Hill tinkering with legislation, conducting what amounts to a sneak attack on the environment," said Interior Secretary Babbitt.
It is a "sneak attack" because in most cases the changes are not directly in environmental laws but in the way those laws are implemented.
"The two most dangerous changes are the requirement for risk assessment and compensation for takings," said Gregory Whetstone, legislative director of the Natural Resources Defense Council.
This legislation, pending in the Senate, requires an extensive assessment of risk, cost and benefits before a regulation can be made. "The goal is just to make it more difficult, nearly impossible to regulate," Whetstone said.
The "takings" bill requires federal compensation if a regulation reduces the value of private property by 20 percent or more. The effect of this bill, environmentalists said, would be to make it too expensive to protect wetlands and forests.
While these changes might hamper environmental rules, critics, including some in business, warn that they will not make things simpler but will add more bureaucracy and possible litigation.
"The goal shouldn't be getting rid of government," said Hart, "but rather the creation of goal-oriented regulation, relying on competitiveness and innovative capacity."
EDF's Krupp agreed. "People want a cleaner environment. They don't want to be told how to do it. Government should back off as long as there are ironclad guarantees that it will be done."
Wharton's Rosenthal said that ultimately "it isn't an issue that can be settled by science and economics. There is no risk assessment or cost benefit analysis that gives us an answer. It is an issue of values."
"Ultimately," Babbitt said, "the American people are going to have to decide whether they want to accept the changes that are going on in Washington and how important the environment is to them. It is in their hands."