TWENTYNINE PALMS >> Joshua Tree National Park, the nation’s 15th largest, is poised to grow by more than 20,000 acres early next year.

After a lengthy study and environmental assessment, the National Park Service recommends adding more than 20,000 acres of federal, state and private lands to the boundary of Joshua Tree National Park.

The majority of the land — all of it in Riverside County — is in the Colorado Desert, a low elevation and area too hot with too little rain for the park’s iconic plant, the Joshua tree.

This land, which includes the Eagle Mountain and Chuckwalla Valley areas, is of vital importance for the bighorn sheep and desert tortoise populations, a National Park Service statement said.

The area also includes prehistoric and historic resources that expand on the national park’s cultural themes and contains areas important for maintaining Joshua Tree’s wilderness values, the statement said.

The earliest this addition to Joshua Tree National Park could occur is in late February, said David Smith, park superintendent.

Originally, the land was included in the creation of Joshua Tree National Monument by President Franklin D. Roosevelt in 1936, but removed for mineral extraction activities in 1950.

During its mining heyday, iron ore was sent by train from the Eagle Mountain area to the Kaiser Fontana steel mill, where much of the finished product traveled by rail to shipbuilding activities in the Port of Long Beach, Smith said.

Major mining activities ceased in the area in 1983, the Park Service said in a statement.

In 1989, the area was proposed for a landfill. After decades of litigation, the landfill proposal was withdrawn in 2012.

The Park Service and federal Bureau of Land Management, which now administers most of the land, will evaluate public comments on the proposed transfer of the land from the bureau to the Park Service.

If the Department of the Interior determines that it is appropriate to proceed with the transfer, then it will authorize the publication of a public land order in the Federal Register.

A public hearing to discuss these proposed actions will be held from 6 to 9 p.m. Jan. 18 on the UC Riverside Palm Desert campus, Smith said.

Adding this land to Joshua Tree National Park also could be accomplished through congressional Action, Smith said.