In 1987, Chicago Mayor Harold Washington approved funding of a new central library project. Construction began a year later, and the library opened its doors to the public in 1991. Named after the first African-American mayor of the city, Harold Washington Library is has 10 floors, and even after several hours I was only able to see a small section of the building.
It was interesting seeing how the climate of Chicago compared to that of San Diego has shaped the architecture of each library's architecture. The Harold Washington library is much more self-contained; it's all in one big rectangular building that takes up an entire city block, and it's well insulated but doesn't have much natural light throughout the building. Conversely, the Central Library in San Diego has a much more open feel, with different balconies and terraces and several buildings combined into one large library complex.
What holds constant, however, is that both these libraries are some of the largest public libraries in the country, fairly new, extremely nice, and play an fundamental role in their communities.