First marathon and couldn't possibly have been smoother! From initial registration, to e-mail communication, ease of the phone app, ease of check-in at the expo, friendly staff and volunteers, highly organized for 45,000 runners... I couldn't be more impressed. Truly cannot fault this event in anyway... tee shirt could have been a touch nicer, but a very minor complaint in light of the amazing event that this was!!!! Thank you Chicago Marathon staff for a great introduction to marathon running!