Despite early signs of rain, thousands of people converged in Oakland on Saturday in what organizers are billing as the largest anti-fracking demonstration in U.S. history, calling on Governor Jerry Brown to put an end to hydraulic fracturing in California.

The March for Real Climate Leadership was organized by more than one hundred environmental, health and labor groups across the state, including 350.org, Greenpeace and Food & Water Watch. Organizers chose to hold the event in the city where Governor Brown served two terms as mayor to symbolize the urgency of their call to action.

Hydraulic fracturing, known as “fracking,” is a method of extracting oil and natural gas out of deep underground rock formations using a high-pressure combination of water, sand and chemicals. Environmentalists say fracking exacerbates global warming and drought, and that the method has been linked to numerous health concerns for residents who live near fracking sites.

Currently, California is the country’s third-largest oil producer. Fracking is used in about half of all new oil wells in the state.

“Last year, we asked the governor to come and see the reality of fracking, and he refused,” said Juan Flores, an organizer with the Center on Race, Poverty & the Environment, during a press conference before Saturday’s march. “So we are coming to his hometown instead to deliver the message: We need to ban fracking.”

Flores attended the event as a resident of Kern County, which he said hosts 97 percent of the state’s fracking operations. “These fracking sites are located next door to our homes, schools and food sources,” he said, “and we are suffering the health and environmental effects.”

Brown has long been an advocate of environmental protections and standards, but has not committed to banning fracking in California. He was not present at Saturday’s event. At a press conference on Friday, the governor pointed to the state’s reliance on cars as symptomatic of conflicted interests. “As long as Californians are going to drive 332 billion miles a year and consume 14 billion gallons of gasoline and 4 billion gallons of diesel,” Brown said, “we’re going to have to have a plan that’s comprehensive.”

Saturday’s march followed on the heels of a significant anti-fracking victory in New York, where in December Governor Andrew Cuomo announced a complete ban on the controversial practice.

Protesters gathered at Frank Ogawa Plaza in downtown Oakland for a press conference before marching nearly two miles to Lake Merritt via Telegraph and Grand Avenues, led by indigenous groups and accompanied by the sound of drums, music, and chants of “Ban fracking now!”

Organizers estimated the crowd at 8,000 people. Oakland police estimated about 2,000 people and reported no arrests.

Activists also plan to deliver more than 200,000 signatures to the governor on Monday demanding that he ban fracking immediately, according to a statement from 350.org.

“Governor Jerry Brown wants to position California as a world leader in the fight against climate change,” said Tia Lebherz, an organizer with Food & Water Watch, during the pre-march press conference. “But climate leaders don’t frack, and until Governor Brown stands up to Big Oil and bans fracking in California, he remains a climate change enabler.”