The Mifflin County Library began in 1842 as a paid lending Library. It became the County Library in 1942.
For 114 years the library was located at 13 East Third Street, which is now the United Way building. Its next home on Water Street has since been torn down. The library moved into its current location on North Wayne Street in 1974.
The Mifflin County Library System has two branches: The main branch in Lewistown and the Kish branch in Belleville.
The Mifflin County Library is part of the Central Pennsylvania District Library Consortium. Other member libraries include Centre County Library (Bellefonte), Schlow Centre Region Library (State College), Juniata County Library (Mifflintown), DuBois Public Library, Shaw Library (Clearfield), and Clearfield County Library (Curwensville).