Frank Lloyd Wright was a key figure in the Prairie School of architecture, and Oak Park was his early stage. He set up shop in 1889 with a home and studio and fanned out with client work, gaining prestige as he pushed the boundaries of design and form.
This map displays his home designs from that first studio up to his redesign of the Nathan Moore house in 1925. It's a study in the evolution of the FLW style, from conventional to stunningly original works of architecture.
Besides having these homes Oak Park is home to great institutions that are a great source of further information on the town and Wright's architectural legacy. Those are the Frank Lloyd Wright Trust and the Oak Park Historical Society. I can definitely recommend tour of the FLW home and studio and the walking tour of the surrounding homes.