In 1943, the U.S. government built a secret facility on a New Mexico mesa, about 35 miles from the oldest state capital in the country, to design and assemble the first atomic bombs. The weapons were used at Hiroshima and Nagasaki in August 1945. What remained on that mesa became Los Alamos National Laboratory, which now conducts research across national security, nuclear science, and medicine. The Manhattan Project National Historical Park — run jointly by the National Park Service and the Department of Energy, established in 2015 — puts visitors as close as possible to where that work began, though the Los Alamos sites themselves are accessible only by Department of Energy bus tours. Santa Fe had already survived conquest, revolt, and the railroad's indifference. The mesa above it held something else entirely — a decision that changed the world, made in secret, in full view of the Sangre de Cristo Mountains.
