Multnomah County Library is the public library system serving Portland and Multnomah County, Oregon, United States. A continuation of the Library Association of Portland, established in 1864, the system now has 19 branches offering books, magazines, DVDs, and computers. It is the largest library system in Oregon, serving a population of 724,680, with more than 425,000 registered borrowers. According to the Public Library Association, it ranks second among U.S.