The Annex Building was designed by Wilfrid Polkinghorne ’14, who originally worked as a draftsman and engineer for the Ahmeek Mining Co. and who joined the Michigan Tech faculty in 1921 (he later became the first head of the independent civil engineering department in 1945). Although we know the Annex was built in 1936, it is unclear whether the building was funded through federal New Deal, state, and general operating budgets or through another source. In 1936–37, the University did receive a federal grant through the Works Progress Administration (WPA) for improving the library cataloging system, and this award may have prompted the library expansion and construction of the Annex, though the connection is unclear. The interior, though originally entirely open plan on all three floors, shows a distinct hierarchy in detailing that demonstrates the relative importance of the floors: the basement has rough concrete walls and a dirt floor, the ground floor has simple brick walls, and the second floor has cream-glazed brick walls.
The Annex, originally connected to the AOB by a second-floor bridge, was built during the Great Depression for general storage and expanded library space. The second floor seems to have been dedicated library stack space used mainly for government documents. The basement was used by ROTC as a rifle range until the 1980s and had the building’s only original restroom. After World War II, Army and Air Force ROTC occupied a now-subdivided first floor until they moved to their current building in the 1970s, while the western garage (now the archaeology lab) remained under control of Facilities until the whole first floor of the Annex was turned over to the archaeology program in 1977. The library vacated the second floor in 1966, when they moved into the new J. R. Van Pelt Library building, and from 1971 to 2004, the floor housed a Houghton County Public Health Lab (a non-Michigan Tech entity) and a water-quality testing lab for the Michigan Department of Health and other clients. The main floor was used by Facilities for general storage and, at one time, for housing a pipe shop and a paint shop for the University.
The signature bridge between the AOB and the Annex was removed in 1985–86 (some stories erroneously say the early 1970s) as part of campus renovations, though no single, definitive reason is known for this decision. During renovations to the building in the mid-2000s, no fewer than six reasons for the bridge’s removal were “remembered”: the clearance was too low for delivery trucks and fire/emergency equipment; it was no longer needed to connect the AOB to the library stacks, since the books had been moved to the new library building; the Health Department wanted to insulate itself from the AOB for security reasons; and/or it was structurally unsound.