WASHINGTON -- Climate activists descended on the nation's capital on Sunday in what organizers boasted was the largest climate-change rally in American history, claiming more than 35,000 participants.
The Forward on Climate rally, as it was billed by environmental groups Sierra Club and 350.org, called for President Obama to take immediate action on climate change, with many urging the government to block the oil pipeline known as Keystone XL.
Protesters marched through the streets bearing placards and massed on the National Mall, where speakers addressed the crowd. Washington police declined to provide a crowd estimate.
"Today was one of the best days of my life because I saw the movement come together finally, big and diverse and gorgeous," 350.org President Bill McKibben tweeted after speaking at the rally.
Keystone XL has been a signature issue for climate activists. They caught policymakers and the pipeline industry off guard with protests in 2011 against the proposed pipeline, which would bring so-called tar sands oil from Alberta, Canada, into the U.S. Opponents believe the process to produce and refine tar sands oil would be more carbon intensive than typical oil production, potentially accelerating climate change.
Although other proposed pipelines in the U.S. would shunt larger amounts of oil around the country, the proposed TransCanada project must pass through a legal bottleneck in order to be built: U.S. law requires federal approval for new pipelines crossing international borders, making the pipeline more vulnerable to concentrated political pressure.