Are Sim for unlocked mobiles available at O'hare International Airport in Chicago?

Basically, I would like to know if coming from abroad having an unlocked phone, there are pre-paid sims available at the airport? In other countries you just need to buy there sim card install it in your phone and your good to go. But I hear in Chicago you need to activate your phone with one of the available Telecom companies like T-Mobile or something.