[6] The More Hall Annex was a two-story, reinforced concrete structure designed in the Brutalist style, similar to other buildings on the university campus built during the post-war era.

[1][2] The building was designed by a consortium of UW faculty members, known as The Architect Artist Group (TAAG), with input from nuclear engineering department chair Albert L. Babb.

Babb requested a building that would "show the world what nuclear power looked like", desiring a prominent structure on the campus that would serve as a crown jewel for the department.

[7] The first floor, partly covered by the outdoor plaza, housed the reactor, laboratory, crystal spectrometer, counting room with a nuclear densometer, classrooms, restrooms, and offices.

[2] During the late 1950s and 1960s, the Atomic Energy Commission (AEC) provided universities and colleges with grants to acquire small nuclear reactors for research programs.

In 1957, the AEC approved $100,000 in funding (equivalent to $830,000 in 2023 dollars)[9] for the University of Washington to install a permanent nuclear reactor on the campus, the first of its kind in the United States.

[3][10][11] The proposed 10 kW reactor was approved by the university's Board of Regents in April 1959, to be housed in a two-story reinforced concrete building with offices, workshops, a control room, and class and seminar spaces.

[4] It was officially dedicated on June 1, in a ceremony attended by Argonne National Laboratory director Norman Hilberry, a physicist who worked on Chicago Pile-1, the world's first nuclear reactor to achieve criticality.

[20] One of the workers, graduate student W. Robert Sloan, was exposed to 42 milligrams (0.65 gr) of plutonium dust and drove to a laboratory in Richland to be tested for radiation, but was found to have not been significantly contaminated.

The spill was later linked to vibrations in the capsule holding the sample,[21] and workers credited good design and careful handling in avoiding a larger incident.

[34] The structure was added to the National Register of Historic Places in 2009, based on an application submitted by Abby Inpanbutr (née Martin), a UW architecture student, in spring 2008.

[38] The university released a draft supplemental environmental impact statement (SEIS) for the project in October 2015, recommending the demolition of the More Hall Annex in their preferred alternative.

[46] On February 11, 2016, the UW Board of Regents approved a site plan that would demolish the More Hall Annex to allow for the construction of the new computer science center, to open in 2019.

[47][48] An attempt to incorporate elements of the nuclear reactor into the new computer science building was rejected because of the impact of potential seismic retrofits that would be required to meet modern standards.

[50][51] Demolition of the More Hall Annex began on July 19,[52] and preservationists held a mock funeral for the building with Daniel Streissguth, one of the project's original architects.