( CNN ) -- Half a million acres will be protected Wednesday when President Barack Obama establishes the Organ Mountains-Desert Peaks National Monument . It 's `` a once-in-a-lifetime opportunity '' to head off development on the swath of land in south-central New Mexico that has `` unique Pre-American , New Mexican , and American history , '' the monument 's official website says . For Obama , signing a proclamation Wednesday at the Department of the Interior will bring to fruition a promise in his 2014 State of the Union address : `` I 'll use my authority to protect more of our pristine federal lands for future generations . '' White House spokesman Jay Carney said , `` By establishing the monument , the President will permanently protect more than 496,000 acres to preserve the prehistoric , historic and scientific values of the area for the benefit of all Americans . '' Carney cited an independent study that found the monument could generate $ 7.4 million `` in new economic activity annually from new visitors and business opportunities , while preserving access for sportsmen , ranchers and recreational users . '' The monument is apparently smaller than what some in New Mexico had sought . A proposal had called for 600,000 acres to be protected , according to the website . The United States has 77 other national monuments , according to the organization National Park Advocates , which operates nationalparkstraveler.com . Some were created by acts of Congress ; others by presidential proclamation . The Bureau of Land Management operates 19 national monuments across nine Western states , including Arizona , California , Colorado , Idaho , Montana , New Mexico , Oregon , Utah and Washington . In October 2012 , Obama established the Cesar E. Chavez National Monument in California . Scientists : U.S. historic landmarks imperiled by climate change .
The Organ Mountains-Desert Peaks National Monument will include nearly 500,000 acres . Hide Caption President Obama established the Cesar E. Chavez National Monument in 2012 .