th 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-ann