It is a full-service library and is ADA compliant. As with all libraries in the Chicago Public Library system, it has free Wi-Fi internet service. The building contains approximately 756,000 square feet (70,200 m2) of space. The total square footage is approximately 972,000 square feet (90,300 m2) including the rooftop garden penthouse, according to the Zoning department of the city of Chicago.
With the support of Harold Washington and Chicago's wealthy Pritzker family, ground was broken at the chosen site at Congress Parkway and State Street, covering an entire block. Upon the building's completion in 1991, the new mayor, Richard M. Daley, named the building in honor of the now-deceased former mayor Harold Washington, an advocate of reading and education among Chicagoans as well as an advocate of the library's construction.
Before 1872, Chicago had mainly private libraries. England responded to the Great Chicago Fire of 1871 by donating over 8,000 books to the city, which became the foundation of the first public library. This collection was housed in a variety of locations, until the Central Library was built in 1891.
The Harold Washington Library opened on October 7, 1991. Since completion, the library has appeared in the Guinness Book of Records as the largest public library building in the world.
According to wikipedia