President Joe Biden will designate two new monuments on Tuesday, creating the largest tract of protected land in the mainland United States by extending a corridor west, the White House said.

The proclamations Biden plans to sign would create the Chuckwalla and Sáttítla Highlands national monuments, with the former located in Southern California and the latter in the northern mountainous portion of the state.

According to the administration, the two new monuments cover a total of nearly 850,000 acres.

Chuckwalla National Monument, being constructed south of Joshua Tree National Park, forms the new Moab-Mojave Conservation Corridor, a nearly 18 million-acre area of ​​protected land stretching about 600 miles from Southern California to Utah – the largest in the Lower Country According to the White House, there are 48 states.

The Chuckwalla will protect 624,000 acres of land, “preserving critical habitat for endangered and rare species and ensuring that the ancestral homelands and sacred cultural legacies of the region’s tribal peoples are preserved,” the White House said.

The monument will protect the ancestral homelands of the Cahuilla, Chemehuevi, Mojave, Quechan and Serrano Nations.

The monument’s habitat includes 50 rare plant and animal species, including the desert bighorn sheep and its namesake, the chuckwalla lizard.

Sáttítla Highlands National Monument, meanwhile, will protect 224,000 acres, including portions of the Modoc, Shasta-Trinity and Klamath national forests, the White House said, and also the dormant Medicine Lake volcano, which has an area 10 times larger than Washington’s Mount. St Helens.

The land protected by this monument is also home to rare and endangered plants and animals, including the Cascade frog, long-toed salamander, and tawny owl.

The Interior and Agriculture departments said Biden used his authority under the Antiquities Act to designate these monuments.

In 2017, Trump decried previous use of the 1906 Land Conservation Act and dramatically reduced the size of several national monuments during his first term.

The White House said Biden’s new designations “mark a capstone to four years of historic progress in conservation.”

The move comes a day after Biden issued a sweeping ban on all future oil and natural gas drilling on 625 million acres off the coasts of the U.S., including the entire East Coast, the eastern Gulf of Mexico and the Pacific Ocean off the coasts of Washington, Oregon and California and parts of the northern Bering Sea in Alaska.