The William Cardinal O'Connell Branch Library is a publicly funded and managed library that serves more than 110,000 residents in the city of Cambridge, across the Charles River from Boston in Massachusetts. It is an affiliate branch of the Cambridge Public Library, founded in 1991. The William Cardinal O'Connell Library branch contributes to the overall collection and services of the library system, which include more than 300,000 book and serial volumes, more than 21,000 e-books, more than 20,000 audio files, and more than 36,000 video files. Additionally, the library system circulates more than 1.5 million items, has more than 57,000 registered borrowers, and receives almost 900,000 visitors annually across its seven locations.