SAN DIMAS -- Standing under hot and hazy skies with the San Gabriel Mountains behind him, President Obama set aside 346,000 acres of U.S. forestland as a national monument Friday.

Calling it “an issue of social justice,” Obama said that “for a lot of urban families, this is their only big outdoor space.”

“The story of the San Gabriel Mountains is, in many way, the story of America,” the president said. “It’s the story of communities exploring the Great West.”

The decision to provide new federal protections for the area, which accounts for 70 percent of Los Angeles County’s open space, drew plaudits from lawmakers and community groups even as it sparked a small protest by the grounds of the county park where Obama was speaking.

Belinda Faustinos, deputy chair of the San Gabriel Mountains Forever, called the move “a victory for our community.”

“For Latinos, this is especially significant,” Faustino told the audience, adding that there are “extreme pockets of disadvantaged communities who now will be able to access these mountains.”

While land rights groups and some residents have warned the new status could lead to restrictions on what activities can take place on the mountain range, Rep. Judy Chu (D-Calif.) said the designation would increase the flow of federal dollars to the area.

“This will not take away water. This will not take away off-road vehicle use,” said Chu, who introduced legislation in June to make the area into a national recreation area. “Instead, what we will have are more resources to deal with the challenges that come with the recreational use that’s up there.”

On Friday Agriculture Secretary Tom Vilsack announced the U.S. Forest Service would invest more than $1 million in additional education staff and maintenance work on the monument’s trails and picnic areas. Private groups can now provide designated funds to the monument: the National Forest Foundation announced it will commit $3 million, while another group of foundations pledged to raise $500,000.

But Chuck Cushman, who heads the American Land Rights Association, said the Forest Service was merely taking money from the same budget it uses to support all U.S. forests.

“Obviously the monument process is one area where democracy and public participation doesn’t matter,” Cushman said. “We’re going to make the Democrat members of Congress responsible for these monuments. These congressmen and these senators can stop them if they want.”

Brian O’Donnell, executive director of the Conservation Lands Foundation, said the president’s decision to create a 13th national monument had broad public support.

“Californians aren’t the only ones celebrating this new national monument, all Americans benefit when their voices are heard and [he] acts in the long-term interests of the nation,” he said.