The nation's newest monument covers 342,177 acres of the Angeles National Forest and 4,002 acres of neighboring San Bernardino National Forest. The area is within 90 minutes of 15 million people in the Los Angeles Basin.

The designation will help ensure these lands remain a benefit for all Americans through rock art that provides a glimpse into ancient civilizations, an observatory that brought the world the cosmos, and thousands of miles of streams, hiking trails and other outdoor recreation opportunities.

Soaring high above the Los Angeles Basin, the San Gabriel Mountains also are working lands that provide Angelenos 70 percent of their available open space and 30 percent of their drinking water. The monument serves as the backyard to the nation's second-largest urban center.