The People's Climate March was a large-scale activist event to advocate global action against climate change, which took place on Sunday, September 21, 2014, in New York City. With an estimated 311,000 participants, it was the largest climate change march in history. Described as "an invitation to change everything," the march was called in May 2014 by 350.org, the environmental organization founded by writer/activist Bill McKibben, and it was endorsed by "over 1,500 organizations, including many international and national unions, churches, schools and community and environmental justice organizations." It was conceived as a response to the scheduled U.N. Climate Summit of world leaders to take place in New York City two days later, on September 23. Although based in New York, the event was intended to be global in scope and implication, and there were "companion demonstrations" worldwide. Organizers intended the march to be "the largest single event on climate that has been organized to date… one so large and diverse that it cannot be ignored."