Organ Pipe National Monument, Arizona — A remote desert region along the southern border has become a makeshift international arrivals area for thousands of migrants from Africa, Asia and Latin America hoping to work and reunite with family members in the U.S. Over the past few days, large groups of migrant men, women and some families with children have spent the night in a makeshift staging ground in this rugged section of the U.S.-Mexico border, waiting for overtaxed border officials to process them. Many expect to be released into the U.S. after being vetted by local Border Patrol agents, who...