The library was designed by Arthur Howell Brockie (1875–1946) and his partner Theodore Mitchell Hastings (1876–1950). Brockie, educated at the University of Pennsylvania, apprenticed with Cope and Stewardson, and founded his Philadelphia architectural firm with Hastings in 1904. Hastings attended Harvard and trained at the Ecole des Beaux-Arts in Paris. In partnership until 1918, their practice consisted primarily of hospitals and institutional buildings. For this commission, they used local stone quarried on the Fox family's land and built a combination library and auditorium building as requested by Hannah Fox. The two stories built against the hillside offer entrances at river level for the library and at hillside level for the auditorium. The auditorium, Lincoln Hall, has been refurbished and updated to host the Allegheny Riverstone Center for the Arts (ARCA), and houses a Wurlitzer organ manufactured in 1909.
The building's tiled roof and inset balcony overlooking the river evoke an Italian Renaissance palace with a strict rectangularity and formality in the windows and paired columns supporting the balcony roof. Random stonework combined with formal quoins and a stone course above the first-story windows emphasize this unusual marriage of materials and stylistic intention. Typical of the architectural eclecticism of the era in which it was designed, the interior of the library is furnished with oak Mission-style tables, chairs, and interior trim.