The Chicago Astronomical Society is the oldest astronomical society in the western hemisphere, started in 1862. To this day, CAS continues to further its mission by maintaining an observatory, offering numerous venues for public outreach, conducting public observing sessions, and hosting monthly meetings and lectures. CAS also puts on two annual festivals each year: the Earth, Wind & Sky Festival and Astrofest. Click on the links to the left for more information about each of these. 

Related Website: http://www.chicagoastro.org/