San Bernardino National Wildlife Refuge protects a rare desert water landscape on the U.S.-Mexico border in southeastern Arizona. Established in 1982, it preserves part of the Yaqui River headwaters and habitat shaped by springs, seeps, and a fragile aquifer in the Basin and Range region. After settlement in the late 19th century, farming, mining, and livestock production lowered the water table, altered wetlands and grasslands, and eliminated many native fish locally. The refuge became crucial for conserving endangered aquatic species found nowhere else in the United States, but its future remains vulnerable because border wall construction has drained artesian wells and disrupted wildlife movement.