SAN DIMAS Calif. (Reuters) - President Barack Obama on Friday declared large parts of the San Gabriel Mountains near Los Angeles as a national monument and vowed to protect more federal lands for future generations.

With the mountains providing a scenic backdrop for Obama's announcement, the president cast his decision as one of social justice, saying the area is the only close outdoor space for urban families in the outer suburbs of Los Angeles.

"It reminds us that America belongs to all of us, not some of us," Obama said.

The San Gabriel Mountains have a rich history in American lore. Gold Rush prospectors went there, looking to get rich quick in the 1800s. Edwin Hubble, namesake of the Hubble telescope, studied the heavens from a nearby observatory.

Obama noted he has designated 3 million acres of federal land for protection. "And I am not finished," he said.

He said he would particularly look at areas where the local community has called for action.

Designation of the area as a national monument followed an 11-year effort that got caught up in partisan politics.

Along with the designation, the U.S. Forest Service will dedicate $1 million for educational staff, graffiti removal and other long-deferred maintenance work, and non-profit foundations have committed an additional $3.5 million for restoration and stewardship of mountain areas.

The declaration was made at the request of Democratic Representative Judy Chu, whose legislation to protect the area is stuck in Congress along with other wilderness bills as Republicans and Democrats feud.

The 540-square-mile (1,400-square-km) section of the Angeles National Forest to be protected under the order attracts 3 million visitors a year, but graffiti mars the landscape, and the U.S. Forest Service has little money for signage or even restroom repair, said Chu, whose district includes part of the area.

Legislation to protect the mountains has been introduced twice in Congress, once in 2003, leading to a 10-year-study by the U.S. Park Service, and then in June 2014, when Chu submitted a bill to designate them a national recreation area.

After her bill became stuck in a subcommittee, Chu asked Obama to use his executive authority to declare part of the area a national monument.

That angered some local officials and many Republicans, who said it was an end-run around Congress.

Judy Nelson, mayor of the foothill city of Glendora, said naming the area a national monument instead of a national recreation area could invoke different environmental protection rules and might harm businesses.

Obama's declaration will affect only land already designated as a national forest, and will not include San Bernardino County, whose governing body voted to oppose the action.

(Reporting by Sharon Bernstein in Sacramento, Calif.; Editing by Peter Cooney and Ken Wills)