The lines west out of Chicago were sold off, but I don't remember to who or when. There was a while it seemed that ICG was trying to abandon or sell off everything they owned except Chicago-Memphis-New Orleans. Picture that when they sold off the Alton, they even sold off the only remaining Chicago to St. Louis line, as the old ICRR line had been pulled up south of Cimic and a short connection built in Springfield IL so ICRR side trains could get on the GM&O to go south.
It was said at the time of the IC+GM&O merger that the combined company had more miles of railroad in Mississippi than they did in Illinois. They cured that situation fairly quickly by basically abandoning everything they could and selling off what they couldn't abandon. It was suspected by many and well proven by event that the only thing the ICRR wanted out of the GM&O was tu eliminate a competitor. Considering that about the only piece of GM&O remaining in ICRR hands is the ex GM&N line into Mobile, I think that has certainly proven true. Yes, there is also Chicogo to Joliet, but that was kept more to keep the Alton buyers from being able to access Chicago than anything else. Same way they kept the buyer of the old M&O out of Mobile. The Yankees finally did get big chunks of the M&O torn up, but it took them over 100 years to do it.
It is one outstanding example of taking a great company with a great system and running it completely into the ground.
The merger was signed in Jackson, Mississippi. If the people of the state had any idea what the future held, the ICRR people would have been ridden out of town on a rail, of the fence kind with a coat of tar. Ike Tigrett must be spinning in his grave.