Industrialist Andrew Carnegie built 2,509 public libraries between 1883 and 1929. 1,689 were in the United States. Other countries that benefited were primarily United Kingdom, Ireland, and  Canada in addition to Australia, South Africa, New Zealand, Serbia, Belgium, France, the Caribbean, Mauritius, Malaysia, and Fiji.

Having had made a fortune through tireless ambition and nearly cornering the steel industry, Carnegie later turned to philanthropy. He believed in giving to the "industrious and ambitious; not those who need everything done for them, but those who, being most anxious and able to help themselves, deserve and will be benefited by help from others." Under segregation, black people were generally denied access to public libraries. Rather than insisting on his libraries being racially integrated, Carnegie funded separate libraries for African Americans in the South. Carnegie's grants were very large for the era, particularly for small towns where the library often becomes the cultural center. His Carnegie Libraries project is one of the costliest philanthropic activities, by value, in history.

Carnegie also made another significant contribution to Tucson, the Tumamoc Hill Research Station. More of this can be found on page 65 in the reference found here.

Due to the quality of design, materials, and construction, nearly all of the Carnegie Libraries have become National Landmarks. The preferred architecture plan was formal and classical; however, the entrance needed to be designed to welcome patrons to enter. The use of a prominent doorway was accessed via a staircase from the ground level. The entry staircase symbolized a person's elevation by learning.

Tucson’s library was made possible by a $25,000 gift from the Carnegie charity. In contrast, the Washington D. C. library was funded $300,000. The Tucson City Council committed to providing $2,000 annually to supporting the operations. The prior Carnegie library book collection was housed in City Hall.

Bids for the design were submitted by three Tucson firms and four from out of town. Henry C. Trost won the competition. He admired the entrance design by another Tucson architect, Robert F. Rust, and he asked Rust to join him in his business. They became Trost and Rust in 1902. The prescribed Classical Revival architectural style for the new library was a departure from the innovative Southwest and Mission influences that Henry Trost was experimenting with in Tucson at the time. A cornerstone of blue marble was placed in 1900. The 4,000 square foot library was completed by local stonemasons in 1901. The central rotunda was crowned with a copper dome. The original stone was quarried from Sentinel Peak and had a reddish tint. The entrance faced east toward the Armory Park Plaza and the color of the stone was favored so to harmonize with the red sandy soil of the plaza in the morning sunlight. Central Iconic columns mark the entrance of the porch flanked by buff brick square columns. This theme, backed by arched entrances, was repeated for the facades of the two wings. The original entrance was graced overhead by a “pediment tableau”; a triangular gable with an inset relief with depiction of scenes portraying higher learning. Gustave Vierold was the master sculpturer. The original Trost design provided separate reading rooms for ladies and gentlemen. The image below is the rear of the building where the semi-circular wall follows the contour of the book shelves of the original design.

Trost would return to employ some of these design components for the adjacent Scottish Rite Cathedral a decade later. Terra Cota ornamentation and galvanized iron cornices added flair to the parapets.

Beniamino Bufano was commisoned to install an impressive 22-foot curved marble arched bench in 1920 and it is still seen today. This is considered possibly the oldest public art in Tucson. Italian-born Bufano (October 1890 to August 1970) worked extensively in California. Merrill Freeman, a prominent Tucson banker, donated the $11,000 for the bench along with his collection of 5,000 rare books.

A children’s room was added in 1924. Newspaper articles indicated this created some disgruntlement by the older patrons

The library was doubled in size in a 1938 renovation project funded by the depression era Roosevelt Public Works Administration. These funds saved the library from being demolished and provided many jobs for local tradesmen.

A piece of popular trivia involves the loss of two griffins during this 1938 work. Think Harry Potter? A griffin is a winged lion, a mythical creature dating to the Greeks. Rather than replace the griffins, footprints of the griffins can still be seen in the sidewalks leading from the library as they ran off. The griffins are honored today by the red LED lit Joe O’Connell sculpture one block south of the library on Scott Street.

The library dome collapsed in a 1941 fire in the semi-circular bookshelf area in the back of the building. The roof was replaced with a flat roof. The ornamental triangular pediment details over the entrance were also lost and are covered smooth plaster today. Most of the books survived except unfortunately the Freeman rare book collection were lost. The book inventory grew to 60,000 volumes after the 1942 fire reconstruction.

On January 7, 1957, the name was changed to the Tucson Public Library. Over time Pima County assumed operation duties of the local libraries and the name changed to the Tucson-Pima and later the Pima County Libraries. More rooms were added over the years. In 1961 a trend in the modernist movement attempted to erase the remaining historic nature of the building. Over detailed ornamentation was viewed as an anachronism. Large metal gates were added on the perimeter of the entrance to prevent “winos” from loafing around the front of the building.

The main library was opened in 1970 so the Carnegie building was selected to serve the community as the Children Museum Tucson.