The world's first atomic blast and how it interacted with the Jornada Del Muerto and Chupadera Mesa
— Thomas E. Widner

Because of the complexity of the implosion-assembled bomb developed at Los Alamos, a test was considered necessary. To preserve the secrecy of the atomic bomb mission and avoid claims against the Army, residents of New Mexico were not warned before the blast or informed of residual health hazards afterward, and no residents were evacuated. The device was detonated close to the ground, causing much soil to be drawn into the fireball. Some melted soil aggregated into larger droplets that became too heavy to remain suspended, fell to the shot crater, and formed puddles that cooled and became popular souvenirs known as trinitite or atomsite. Most material taken into the fireball eventually came to the surface as radioactive fallout. Exposure rates measured up to 15 or 20 R h^-1 in public areas about 20 mi northeast of ground zero. Field teams used instruments that were crude, ill suited to field use, and incapable of measuring about 4.8 kg of unfissioned plutonium that was dispersed. Vehicle shielding and contamination were not corrected for. Terrain and air flow patterns caused “hot spots” in and around Hoot Owl Canyon, which became known as “Hot Canyon,” and on Chupadera Mesa. Key residences were unknown to the Army and were not visited on test day. Ranchers reported that fallout “snowed down” for 4-5 d after the blast. Many residents collected rain water off their metal roofs into cisterns for drinking. It rained the night of test day, so fresh fallout was likely consumed. Most ranches had one or more dairy cows and a ranch near Hot Canyon maintained a herd of 200 goats. All evaluations of public exposures from Trinity published to date have been incomplete in that they have not reflected the internal doses that were received by residents from intakes of airborne radioactivity and contaminated water and foods. Too much remains undetermined about exposures from the Trinity test to put the event in perspective as a source of public radiation exposure or to defensibly address the extent to which people were harmed.