"Now we are all sons-of-bitches." --Dr. Kenneth Bainbridge, Director of the Trinity Test On July 16, 1945, at 5:29:45 a.m., the first atomic explosion in history took place at the Jornado del Muerto (Journey of Death) trail on the Alamagordo Bombing Range in New Mexico. An extremely tense group of scientists looked on as the bomb, named "Gadget," released its 18.6 kiloton yield, vaporizing the 100-foot steel tower it had been hoisted atop. At 33 degrees North latitude, Operation Trinity carried mankind into the atomic age. The Trinity mushroom cloud rose to a height of 33,000 feet into a northeast wind which blew a 50-kilometer-wide pattern of radioactive fallout more than 150 kilometers from Ground Zero. A ten-mile stretch of U.S. Highway 380 received approximately 50 R of radiation exposure -- a significant dosage, but below the threshold for short-term health effects. Another area, dubbed "Hot Canyon," received more than 200 R. The site was just 5 miles east of Bingham, New Mexico, and about a mile from a road junction. Radiation exposure reached a total of 60 R in the backyards of two families who lived within a mile of "Hot Canyon;" they were not evacuated. Some evacuations did take place along the path of the drifting fallout cloud, where radiation levels reached 15 R per hour following the detonation. Burns caused by beta radiation were observed on cattle in the vicinity of the test. A month after the Trinity test, the Japanese cities of Hiroshima and Nagasaki were incinerated by the "Little Boy" and "Fat Man" bombs, killing nearly 200,000 people, most of them civilians. Yet it is interesting to note that the first people to be exposed to radioactive fallout were, in fact, U.S. citizens. NEXT: Operation Crossroads