Mr. Biden has so far created five national monuments and expanded two others, part of his pledge to conserve 30 percent of the nation’s lands and waters by 2030. He has also sought to embrace the intersection of conservation, climate and Native American issues. Native American voters could play a significant role in the election outcomes in the swing states of Arizona and Nevada.

Last year, Mr. Biden gave a national monument designation to half a million acres of the Spirit Mountain area in southern Nevada. Also known as Avi Kwa Ame, it is the mythical creation site for Yuman-speaking tribes like the Fort Mojave, Cocopah, Quechan and Hopi. In 2021, he restored and slightly expanded the 1.3 million acres of Bears Ears, a national monument in Utah and the ancestral homeland of five tribal nations that had been slashed in size by the Trump administration.

To date, Mr. Biden has preserved more than 41 million acres of land and waters.

The San Gabriel monument encompasses 342,177 acres of the Angeles National Forest and 4,002 acres of neighboring San Bernardino National Forest. Mr. Biden will expand the monument by approximately 110,000 acres. The expanded national monument includes a unique scenic railroad, grand recreation resorts and Nike missile facilities that date from the Cold War.

The Berryessa Snow Mountain National Monument includes nearly 331,000 acres of protected land in parts of Napa, Yolo, Solano, Lake, Colusa, Glenn and Mendocino Counties. It would be expanded by about 13,753 acres under Mr. Biden’s plan. The new designation protects a striking 11-mile-long ridgeline that features unique geologic and hydrologic features and is sacred to the Patwin people. The presidential proclamation also permanently renames the ridgeline, previously known as Walker Ridge, to Molok Luyuk, which means Condor Ridge in the language of the Patwin people.

“Molok Luyuk is sacred to the tribes who have long advocated for its protection and maintain a deep connection with this land and thanks to President Biden’s leadership, it will now be protected for future generations,” said Interior Secretary Deb Haaland, the nation’s first Native American cabinet secretary.