- A multitype library system serving (i) a minimum of 150,000 inhabitants or (ii) an area of not less than 4,000 square miles and serving a minimum 10 or more public libraries, elementary, and secondary school libraries, institutions of higher education libraries, and special libraries.
- A public library system consisting of a single public library serving a city of over 500,000 population.
- A multitype library system that serves the same territory as a library system under subparagraph (2) of this definition that provides service to elementary and secondary school libraries, institutions of higher education libraries, and special libraries. "Special library" includes, but is not limited to, libraries with unique collections or specialized services recognized by the State Library.
There are three library systems within Illinois: Chicago Public Library System, Illinois Heartland Library System (IHLS), and Reaching Across Illinois Library System (RAILS). Library systems in Illinois are funded by annual-system-area and per-capita-grants from the Illinois State Library. These funds are used to serve the communities that make up each library system’s service area.
There are four types of libraries: public, school, academic, and special. Some of these library classifications contain subtypes. Definitions and subtypes of these four library types can be found below.
More than 600 public libraries exist within the state of Illinois. Public libraries can be broken down into three statutory categories:
- Local libraries – Local libraries include city, village, town, and township libraries. According to the Illinois State Library, local libraries are “semi-autonomous municipal corporations organized under the Local Library Act [75 ILCS 5/1-1 et seq.].”
- County libraries – Illinois libraries can be created by election to serve an entire Illinois county. However, none currently exist within the state of Illinois.
- District libraries – Public library districts are “wholly independent local government units, sometimes referred to as a ‘special taxing district,’ organized under the Library District Act [75 ILCS 16/1-1 et seq.].”
A school library is a library that serves an institution of primary or secondary education. Usually serving one or more grades from kindergarten through 12th, these libraries can be part of public or private institutions and can serve a single building or an entire district.
An academic library is a library that is attached to a higher-education institution, such as a college or a university. The purpose of academic libraries is to:
- Support the college/university curriculum
- Serve as a research hub for both the faculty and the student body
A special library focuses on specialized information resources. Instead of covering many different areas of interest, like an academic library, a special library will have one main area of focus. Examples of special libraries include, but are not limited to:
- Medical libraries
- Law libraries
- Museum libraries
- Government libraries
- Corporate libraries