Get Your Code On at API Hackday Chicago on May 28th The first API Hackday was held in San Francisco last October and is being held again in Chicago, bringing together awesome API companies like SimpleGeo, SendGrid, Apigee, Mashery, Twilio, and Morningstar. The event runs from 8 AM – 8 PM and is completely free to attend and participate, but space is limited so registration is recommended.