Chicago is about 42 times bigger than Cocos (Keeling) Islands.

Cocos (Keeling) Islands is approximately 14 sq km, while Chicago is approximately 590 sq km, making Chicago 4,113% larger than Cocos (Keeling) Islands.
Tip: This to-scale comparison of Cocos (Keeling) Islands vs. Chicago uses the Mercator projection, which distorts the size of regions near the poles.