The Chicago Park District has a useful and informative website with photos and links to all the organized activities available in the parks.
Washington Park and other landmarks can be seen from the neighborhood tours available on CommunityWalk.  
If you’re interested in playing team sports in Chicago parks, Players’ Sports, Sports Monster or Chicago Sport and Social Club can match you up with a team.
Chicago leisure and recreation from 1900 to 1930 is extensively and entertainingly documented at the Jazz Age Chicago website.
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Image sources
Lighted windows: Archival Photofiles, apf2-08354, Special Collections Research Center, University of Chicago Library