Correction: An earlier version of this article incorrectly stated that White House counselor John D. Podesta said the designation would influence next month’s midterm elections. He did not anticipate any impact on the elections. This version has been corrected.

President Obama used his legal authority on Friday to designate the San Gabriel Mountains, located in northeast of Los Angeles, as a national monument. (WhiteHouse.gov)

President Obama used his legal authority on Friday to designate the San Gabriel Mountains, located in northeast of Los Angeles, as a national monument. (WhiteHouse.gov)

When President Obama stands in the shadow of the San Gabriel Mountains northeast of Los Angeles on Friday and sets aside 346,000 acres as the country’s newest national monument, he will bring together two of the top priorities of what he hopes will be his presidential legacy — environmental protection and cultural and demographic diversity.

The ceremony — which will mark the 13th time Obama has used his legal authority to designate a monument — reflects a broader White House strategy to preserve public lands that resonate with key demographic groups.

Latino organizations and allied groups have lobbied for nearly a decade and a half to safeguard the San Gabriel Mountains on the grounds that they provide critical green space and fresh water to the area’s large Latino population.

“What we want to ensure, and what the president has focused on, is that all Americans, and the great diversity of Americans, both have the opportunity to access these important places and can experience them” in perpetuity, White House counselor John D. Podesta said in an interview.

The next spot Obama will use his legal authority to protect is Chicago’s Pullman Park district, which commemorates both labor and African American history. The administration is also eyeing other sites, such as a former Japanese American internment camp in Hawaii.

Podesta said he doubted whether Friday’s designation would influence next month’s midterm elections. “Most of the decisions about Congress and governors are not going to be made in Los Angeles County. But I think this will get an enthusiastic response from the Latino community in Los Angeles County, as it should.”

The new monument, which will include parts of the Angeles and San Bernardino national forests, accounts for 70 percent of Los Angeles County’s open space and provides more than one-third of its drinking water. Fifteen million people live within a 90-minute drive, and the mountain range provides critical habitat for imperiled plants and animals, such as the California condor, Nelson’s Bighorn sheep, spotted owl and the mountain yellow-legged frog.

Several local groups and federal lawmakers who represent the area — such as California Democrats Sen. Barbara Boxer and Rep. Judy Chu — have called on Obama to designate the region a monument, but some local officials and national land rights activists have argued that doing so will interfere with private property owners’ rights. The National Park Service conducted a 10-year study on the area, and Chu introduced legislation to create the designation.

Republican House candidate Jack Orswell, who is challenging Chu, wrote in an e-mail that he is concerned that federal authorities will use the designation to “prohibit the use of motorized vehicles, bicycles, horses, shooting sports and mining.”

“As the saying goes, ‘If it ain’t broke, why fix it?’ We don’t need new designations to protect what has been protected for over 100 years,” he said, noting that there are private cabins, a camp and a pack station in the area.

But the Wilderness Society’s Daniel Rossman, who chairs the San Gabriel Mountains Forever coalition, said making the area into a monument will both raise the area’s profile and prompt federal officials to draft a management plan “to protect some of the last remaining wild places” and reduce “the trash, graffiti and safety hazards” that exist now.

Rossman noted that the east fork of the San Gabriel River, which lies in the heart of the Angeles Forest, often violates Los Angeles regional water-quality standards because of the amount of diapers, plastic bags and other waste flowing through it.

Although both Republican and Democratic presidents have used the Antiquities Act to safeguard cultural and ecological sites, Obama has emphasized the historic contributions of Native Americans, blacks and Latinos when he has invoked the law. During his first term, he created national monuments at Fort Monroe, a Hampton, Va., community that served as a safe haven for former slaves during the Civil War; Chimney Rock, a sacred site for Pueblo Indians in Colorado; and labor leader Cesar Chavez’s home. On March 23, he established five more, including one honoring Harriet Tubman’s work on the Underground Railroad on Maryland’s Eastern Shore and the Charles Young Buffalo Soldiers in Ohio.

GOP consultant Alex Castellanos said by e-mail that Obama defines a national monument as “more land the federal government has grabbed so our children can’t enjoy it, either. This president misses very few opportunities to ban energy production, grazing, and any other productive activity he can, any where that he can, just to score political points with his favored constituencies.”

However, Ken Salazar, who as interior secretary commissioned a study of Latino heritage sites, said he “prioritized, and had the president’s complete backing, to make sure we had a more diverse portfolio for the United States of America. . . . When you look at the National Register historic landmarks that celebrate the contributions of women, African Americans, Latinos and Asian Americans, it is appalling. There’s a lot more that needs to be done.”

According to a recent analysis by the liberal Center for American Progress on the country’s 461 national parks and monuments, 26 center on the black community, 19 on Latinos, eight on women, two on Asian Americans and zero on the LGBT community.

While many Republicans have criticized the administration over the San Gabriel Mountains, they have been more supportive of the idea of making Chicago’s Pullman Park district into a national monument. The area, which includes nearly 90 percent of the original buildings that rail car magnate George Pullman built a century ago for his factory town, was the birthplace of the nation’s first African American union.

On Sept. 30, four Illinois Republicans — Sen. Mark Kirk and Reps. Rodney Davis, Aaron Schock and Adam Kinzinger — sent Obama a letter urging him to declare it a national park under the Antiquities Act. Not only did the railroad strike of 1894 lead to greater rights for workers, the lawmakers wrote, but the Brotherhood of Sleeping Car Porters — America’s first African American union — also “helped build the black middle class and laid the groundwork for the Civil Rights movement of the mid-20th century.”

National Park Service Director Jonathan B. Jarvis told Chicago residents in August that he supports making the district a national monument, and Podesta confirmed that the White House was ready to adopt Jarvis’s recommendation. Chicago is the only major U.S. city without a national park unit.

The administration is also looking at potential designations in other parts of the country, including Puerto Rico and Hawaii. It has invited citizens to propose potential sites to expand the National Marine Sanctuaries System, which could lead to additional national monuments.

At the same time, administration officials have told Republican lawmakers that they will hold off making some designations to see if Congress can adopt new protections on its own. A coalition of local residents and national conservation groups has called on the president to expand Canyonlands National Park in Utah because of the effects of offroad vehicle use in the area, as well as grazing and mining activities.

Rep. Rob Bishop, (R-Utah) who chairs the House Natural Resources subcommittee on public lands and environmental regulation, said he is drafting compromise legislation on the issue “so everyone wins something, and nobody gets everything they want.” Both Bishop and Utah Gov. Gary Herbert, a Republican, have spoken to Interior Secretary Sally Jewell on the issue; Bishop said Jewell assured him that Utah authorities would not be surprised by a designation there.

As long as his drafting process is ongoing, Bishop said: “I don’t expect the White House staff, who probably can’t find Utah on the map, to actually do anything.”