Are you asking out of curiosity, or are you trying to figure out the time you need to allow between flights?
If the former, 90 minutes to get through customs/immigration is a good estimate. If someone is meeting you and you have a mobile phone, you will have a window of opportunity to call from when the plane hits the runway until you deplane at arrivals. You CANNOT use your phone while in the customs/immigration area.
If you're trying to decide on connecting flights, it looks like the minimum time for AA for Intl/Dom is 1:10 and on UA it is 1:15, but I would never let anyone book me a connection that tight. I'd allow at least 2 hours between flights.