McDonald ranch house, where the first atomic bomb was assembled, seen fifty years later in 1995. This ranch house has been preserved exactly as it was on the day of the Trinity Test, the detonation of the world's first atomic bomb in July 1945. The ranch house was used for the final assembly of the plutonium core of the bomb. The bomb was detonated at the top of a tower just two miles from the ranch house in the Jornada de Muerte valley, New Mexico. Despite the efforts of the original owners to recover it after World War 2, the ranch house has been kept as a monument to the birth of the nuclear age.