The Free Library of Philadelphia is the public library system that serves the city of Philadelphia, Pennsylvania. It is the 16th-largest public library system in the United States. The Free Library of Philadelphia is a non-Mayoral agency of the City of Philadelphia governed by an independent Board of Trustees as per the Charter of the City of Philadelphia. The Free Library of Philadelphia Foundation is a separate 501(c)(3) non-profit with its own board of directors and serves to support the mission of the Free Library of Philadelphia through philanthropic dollars.