McDonald Ranch House, an adobe ranch house in New Mexico’s Oscura Mountains, became a crucial part of the Manhattan Project when the active components of the world’s first nuclear weapon were assembled there before the Trinity explosion in July 1945. Built in 1913 by Franz Schmidt and later enlarged by the McDonald family, it had served as the center of a remote working ranch until the U.S. Army took over the land in 1942. In July 1945, Manhattan Project personnel converted a bedroom into an assembly room, completed the device there, and sent it to the nearby test tower. Despite damage from the blast, the house survived and was later preserved.