Steve,was that the 1970 New Car Automobile show held in February?
I knew it was always held at the Amphitheatre previously,but starting with the 1970 model year,it was meant to be held at the newly built McCormick place complex,in what's known as the east wing today.Thanks to a fire there days before,they had to move it back into the Amphitheatre again.
Here's some vintage pics from one who was there..
http://www.v8buick.com/showthread.php?t=150479
http://www.v8buick.com/showthread.php?t=150539
http://www.v8buick.com/showthread.php?t=150552