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Tens of thousands of people gathered Sunday on the National Mall in Washington to observe the 40th anniversary of Earth Day and to urge Congress to pass climate and energy legislation.

Major stars were on the roster, including Sting, John Legend, the Roots and Jimmy Cliff, as well as some newer figures like Passion Pit and Joss Stone. (Thursday was the official Earth Day anniversary.)

Some environmental campaigners came dressed as melting polar bears. Others embraced a 1970 theme, wearing tie-dyed shirts or arriving shirtless and shoeless.

Word that senators would delay the unveiling of a climate bill, originally planned with much fanfare for Monday, did not seem to dampen the day, which attracted some 150,000 people over eight hours, according to Tiffany Shipp, a spokesman for the Earth Day Network, the rally’s organizer.

Denis Hayes, who helped mobilize the first Earth Day in 1970 with a small group of environmental activists, said he was gratified by the growing international attention to climate change.

But he complained that lawmakers for the bill that was to be introduced this week — by Senators John Kerry, Democrat of Massachusetts; Joseph I. Lieberman, independent of Connecticut; and Lindsey Graham, Republican of South Carolina — caved to the interests of the coal, oil and transportation industries. (Mr. Graham, angered by the Democrats’ focus on immigration, pulled out of Monday’s announcement, leading to the bill’s deferral.)

Mr. Hayes said the intensity that led to watershed environmental changes decades ago like the Clean Air Act had faded. While dollars flow from lobbyists on both sides of the issue in Washington, he said, American environmentalists must marshal more grass-roots pressure on Congress.

“The whole strategy is inclusivity — there’s something on this stage for everyone today,” he said of the rally. “But, really, recently, we’ve failed on the outside-the-Beltway crowd.”

The Rev. Jesse Jackson; Representatives Chris Van Hollen, Democrat of Maryland, and Ed Markey, Democrat of Massachusetts; and James Cameron, director of the movie “Avatar,” were on the agenda to address the crowd.

What is your view of the nation’s environmental trajectory over the last 40 years? And what kind of climate and energy legislation, if any, would you favor?