General Leslie Groves needed a site at least 200 miles from any international border, west of the Mississippi, and isolated enough to contain the most dangerous secret in human history. Major John Dudley scouted locations in Utah and at Jemez Springs, New Mexico, but none fit. Then J. Robert Oppenheimer, who had spent summers riding horses through the New Mexico mountains as a young man, suggested the Los Alamos Ranch School - a boarding school for boys perched on a 7,300-foot mesa northwest of Santa Fe. Groves took one look and declared it the place. By early 1943, the school had been purchased, its students and faculty sent home, and Project Y had begun. Nobel laureates arrived alongside machinists and military police. Richard Feynman picked locks for fun. Families hung laundry between dormitories while physicists debated implosion designs in converted classrooms. The work culminated on July 16, 1945, when the Trinity test lit up the desert near Alamogordo with the force of 21 kilotons of TNT - the first nuclear detonation in history.

After the war, many expected Los Alamos to shut down. Instead, director Norris Bradbury was tasked with making the hand-assembled bombs mass-producible, turning delicate scientific prototypes into weapons that soldiers could deploy. The lab developed the hydrogen bomb and, for decades, competed with Lawrence Livermore National Laboratory in California on weapons design. But the end of the Cold War forced a transformation. Today, Los Alamos conducts research across an extraordinary range: supercomputing, nanotechnology, space exploration, renewable energy, and genomics. The lab's IBM Roadrunner became the first computer to achieve petaflop speed. Its researchers helped pioneer flow cytometry, a technique now essential to medical diagnostics worldwide. Scientists at Los Alamos have developed ultrasound-based breast cancer detection methods and tested HIV vaccines. The lab's digital epidemiologists use social media data and search queries to predict disease outbreaks in real time.

A facility that has handled the nation's most dangerous materials for eight decades has inevitably accumulated its share of mishaps and controversies. Two criticality accidents in 1945 and 1946 killed scientists working with plutonium cores - incidents later termed the 'demon core' experiments. In 1999, scientist Wen Ho Lee was accused of transferring nuclear secrets to China; after ten months in solitary confinement, 58 of 59 charges were dismissed, and a federal judge apologized for his treatment. In 2000, two classified hard drives went missing from a secure area, only to be found behind a photocopier. In 2011, a management-directed photo shoot arranged eight plutonium rods dangerously close together, nearly triggering a criticality event and prompting the departure of 12 of the lab's 14 safety staff. The lab's 35-square-mile property contains roughly 2,000 contaminated dumpsites, and a 2008 nuclear waste drum rupture at the facility led to a similar incident at the Waste Isolation Pilot Plant near Carlsbad in 2014.

Los Alamos is northern New Mexico's largest employer, with approximately 13,200 direct employees, 1,800 students, and 460 postdoctoral researchers. One-third of the technical staff are physicists, one-quarter engineers, one-sixth chemists and materials scientists. The annual budget runs to approximately $4.9 billion. The laboratory operates three major user facilities: the Center for Integrated Nanotechnologies, the Los Alamos Neutron Science Center with one of the world's most powerful linear accelerators, and a Pulsed Field Facility that is part of the National High Magnetic Field Laboratory. Management has changed hands multiple times - from the University of California's sixty-year direct stewardship through Los Alamos National Security, LLC, to the current operator, Triad National Security, a joint venture of Battelle Memorial Institute, the University of California, and Texas A&M University, which took over in November 2018.

Several Manhattan Project buildings at Los Alamos were designated a National Historic Landmark in 1965, and the Bradbury Science Museum in the town of Los Alamos offers the public a window into the laboratory's history. The lab also gave the world the arXiv preprint server, which it hosted until 1999, and the coreboot open-source firmware project. But the place is defined above all by its original mission. The scientists who gathered on this mesa under wartime secrecy understood they were building something unprecedented. Some, like Oppenheimer, spent the rest of their lives grappling with the moral consequences. Others, like Edward Teller, pushed for ever more powerful designs. That tension - between knowledge and responsibility, between discovery and destruction - still echoes through the pine-covered canyons of the Jemez Mountains, where the atomic age began in a repurposed boys' school at the end of a dirt road.