Two days a year, the site of a once-secret weapon project is open to visitors at the Army’s White Sands Missile Range in New Mexico.

In a few weeks, on April 1, the gate will open for visitors to the Trinity Site, where the first atomic bomb was tested at 5:29 a.m. Mountain War Time on July 16, 1945.

Trinity Site is located in the northern region of White Sands Missile Range, the Army’s leading test facility for missile and space activities.  

The active test facility shuts down some of its operations for the twice-a-year open house at Trinity, according to the Army’s White Sands website.  The next open house will be in October.

Trinity Site was the location for test officers on the Manhattan Project to finalize and test the atomic bomb.

Visitors can see ground zero, where the bomb was placed for explosion, and the McDonald ranch house where the plutonium core of the bomb was assembled. The McDonald house has been restored to the way it looked during the war.  Photos and displays tell the story of the site.

Trinity Site test

The atomic bomb test at Trinity Site, New Mexico.
Photo Credit: Courtesy Los Alamos National Laboratories via U.S. Department of Energy

Soldiers at Trinity Site

Soldiers arrived at Trinity in 1944 to set up the site.

As soldiers do, they made the most of the remote location, playing polo astride horses used for patrols, and hunting deer and pronghorn antelope, which were cooked and served in the mess hall, according to the Army’s White Sands website.

On the website is a history of Trinity Site, which has detailed documents and descriptions.  An excerpt from one narrative from the day of the test:

"Suddenly, my right eye was blinded by a light which appeared instantaneously all about without any build up of intensity. My left eye could see the ball of fire start up like a tremendous bubble or nob-like mushroom," wrote lawyer Ralph Smith, visiting from Los Alamos, New Mexico, where the bomb was designed and built.

What to know when you visit:

  • Entrance is free, and no reservations are required for the one-day open house.
  • Trinity Site is remote, south of Highway 380 between the towns of Carrizozo and San Antonio, New Mexico. Visitors enter through Stallion Gate.
  • The gate is open 8 a.m. to 2 p.m. The site closes at 3:30 p.m. Visitors may arrive and leave unescorted through the gate any time during the open house.
  • To visit, you need a military ID or valid driver’s license, proof of insurance and enough gas in the tank. There aren’t any gas stations in the immediate area, according to the website.
  • Leave your drone at home; no remote controlled vehicles or satellite networking systems are allowed. But you can bring pets, on leashes, just don’t leave them in the car.
  • Concessions and souvenirs are available in the parking lot, where vendors fire up the grill.
  • Radiation levels at Trinity Site are described as low, with a one-hour visit to ground zero involving "a whole body exposure of one-half to one millirem," according to the Army website, or about half the radiation you would encounter on a coast-to-coast flight on a commercial airliner. It’s also about the same as a year’s worth of watching TV, the website notes.

For more information, go to

White Sands' Trinity Site web page

or call WSMR public affairs at 575-678-1134.

About Kathleen Curthoys

Kathleen Curthoys is editor of Army Times. She has been an editor at Military Times for 20 years, covering issues that affect service members. She previously worked as an editor and staff writer at newspapers in Columbus, Georgia; Huntsville, Alabama; Bloomington, Indiana; Monterey, California and in Germany.

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