Founded in 1896, Waterloo Public Library began service in two rented rooms, one on the east side and one on the west side of the Cedar River. In 1906, the Library moved to its new Carnegie buildings which saw extensive remodeling and additions over time. The Library's current building, constructed in 1938, began as Waterloo's post office and federal building. It served as such until 1979 when the post office was relocated. In 1977, Waterloo voters approved a $3,650,000 bond issue to renovate the building for use as a library.
This renovation preserved the modified Italian Renaissance architecture. A two-story addition added garage space, meeting facilities, and additional space for the collection. A new mechanical and electrical system, thermalpane windows, and insulation boosted energy efficiency. The interior of the building now provides the flexible, open space essential for efficient library operation. The building is completely handicapped accessible.
Two murals on the Library's first floor, painted in 1940 by Edgar Britton, were retained during the renovation. A student of Grant Wood, Britton received $2,500 in payment for his work under a New Deal program which funded art in federal buildings. "Exposition" depicts the National Dairy Cattle Congress; "Holiday" is a picnic scene. The murals are tempera applied directly on the walls utilizing the fresco technique. They are considered good examples of the 1930's Midwestern style of regional art.
In 1981, renovations to accommodate the computer system and increase collection space were funded by a gift from the Margaret Nordholm estate. The library held the opening dedication ceremony for its new location on April 26, 1981.
The Youth Department was renovated in the fall of 1994, through a bequest from the Julia Easley estate.
In 2008, the library built the Training Center, a computer lab, funded by Black Hawk County Gaming Association.
In 2016, the library added its makerspace, The Hive, made possible with funding from Black Hawk County Gaming Association, Helen E. Watkins Estate and the Friends of the Library.