Chicago - Question: airside or landside transfer ORD T3 to T1?

Was not sure what section to post this so I figured I'd start here.

I will be making a trip from IAH to PWM via ORD in Nov and will be using AA for the IAH-ORD leg and UA on the other part. (long story as to why 2 diff airlines are being used). But my question is will I have to exit and do the whole security thing again or can I just stay on the airside and make the hike between terminals?

Was not sure what section to post this so I figured I'd start here.

I will be making a trip from IAH to PWM via ORD in Nov and will be using AA for the IAH-ORD leg and UA on the other part. (long story as to why 2 diff airlines are being used). But my question is will I have to exit and do the whole security thing again or can I just stay on the airside and make the hike between terminals?

You can walk from Terminal 3 (AA) to Terminal 1 (UA) inside security. Not
surprisingly, you go through terminal 2. It is a long walk.

http://www.chicagotraveler.com/images/ohare-airport-terminal-map.jpg

As this is less about a specific airline than it is about Chicago - O'Hare International Airport, it will be retitled and moved to the appropriate Forum. /Moderator