The only building in Nevada designed by the New York firm of McKim, Mead and White, the Mackay School of Mines is both architecturally and historically significant. Clarence Mackay built the school as a tribute to the life and career of his father, John Mackay, an Irish miner who found great success as one of the Comstock's four bonanza kings. In 1906 the son hired Gutzon Borglum, who later carved Mt. Rushmore, to erect a bronze statue of his father in front of the building. Located at the north end of the quad, the school and its statue provide a balance for Morrill Hall at the other end. These two anchors give the older campus its distinctive appearance.
The two-story brick building, with Georgian details, has a monumental pedimented stone portico supported by Tuscan columns. White tile in a herringbone pattern lines the portico's ceiling. Double oak doors open to a lateral hallway. The original U-shaped plan included one-story wings projecting from the front core of the building. In 1926 DeLongchamps's remodeling left the front section intact but modified the rear, adding a second story to the wings and filling in the central atrium. The new design included a second-story lightwell immediately behind the front section, providing light for the windows in the original building. DeLongchamps enlarged a mineral museum in the western wing, giving it a dramatic open, two-story space with a surrounding balcony, oak cabinets and balustrade. Overall, he executed the design around existing details so that the modifications did not compromise the original plan.