The ranch house is a one-story, 1,750 square-foot adobe (mud bricks) building. An ice house is located on the west side along with an 9'- 4" deep underground cistern. A 14 by 18.5 foot stone addition, which included a modern bathroom, was added onto the north side in the 1930s.  East of the house there is a large, divided concrete water storage tank and a windmill. South of the windmill are the remains of a bunkhouse, and a barn which also served as a garage. Further to the east are corrals and holding pens for livestock.

The McDonalds vacated their ranch house and their thousands of acres of marginal range land in early 1942 when it became part of the Alamogordo Bombing and Gunnery Range.  The old house remained empty until Manhattan Project personnel arrived in 1945. Then a spacious room in the northeast corner of the house was selected by the Project personnel for the assembly of the plutonium core of the Trinity device. Workmen installed work benches, tables, and other equipment in this large room. To keep the desert dust and sand out, the room's windows and cracks were covered with plastic and sealed with tape. The core of the bomb consisted of two hemispheres of plutonium, (Pu- 239), and an initiator.  According to reports, while scientists assembled the initiator and the Pu-239 hemispheres, jeeps were positioned outside with their engines running for a quick getaway if needed.  Detection devices were used to monitor radiation levels in the room, and when fully assembled the core was warm to the touch. The completed core was later transported the two miles to Ground Zero, inserted into the bomb assembly, and raised to the top of the tower.

The Trinity explosion on Monday morning, July 16, did not significantly damage the McDonald house. Even though most of the windows were blown out, and the chimney was blown over, the main structure survived intact. Years of rain water dripping through holes in the metal roof did much more damage to the mud brick walls than the bomb did. The nearby barn did not fare as well. The Trinity test blew part of its roof off, and the roof has since totally collapsed.

The ranch house stood empty and deteriorating for 37 years until 1982 when the US Army stabilized it to prevent any further damage. The next year, the Department of Energy and the Army provided funds for the National Park Service to completely restore the house to the way it appeared in July, 1945.  When the work was completed, the house with many photo displays on Trinity was opened to the public for the first time in October 1984 during the semi-annual tour. The Schmidt-McDonald ranch house is part of the Trinity National Historic Landmark.

The Day the Sun Rose Twice: The Story of the Trinity Site Nuclear Explosion, July 16, 1945 
by Ferenc Morton Szasz - First published in 1984, this prize-winning history of the Manhattan Project is now available in paperback for the first time, fifty years after the explosion of the first atomic bomb. 
"This tightly focused, lucidly written and thoroughly researched book... describes the events, personalities and scientific processes that led to the detonation of the first atomic bomb in an isolated stretch of New Mexican desert.... Mr. Szasz provides fascinating details.... The Day the Sun Rose Twice is concise and cogent, a valuable introduction to how our nuclear dilemma began." —New York Times Book Review 

"May be the definitive account of the days and hours leading up to the first nuclear explosion in history and the legacy it left. He vividly reconstructs the story: the industrious atmosphere of the scientists and technicians; the grave considerations of those making key decisions; the sense of wonder, and twinges of conscience, at what had been achieved." —Los Angeles Times