Everyone: More 70s era thoughts that come to mind was that the Van Buren and Wells Street (S&W) sections of the Loop were once closed on weekends and there was no thru service to the Loop on the Ravenswood Line on weekends-back then it was a Belmont-Kimball shuttle only...and only the Lake/Dan Ryan trains served the Loop on weekends
on the N&E sections over Lake and Wabash Streets...
More CTA weekend thoughts: The Evanston Line was a shuttle between Howard and Linden and the Skokie Swift was closed for example on Sundays...
I now see that things have changed considerably for CTA riders on weekends...and I should have mentioned the best possible source for CTA history on the Internet:
http://www.chicago-l.org
Thanks to looking in the Loop Elevated section I found these Loop Shuttle dates: Service began on September 30,1969 and was discontinued on September 30,1977...
It ran for just eight years...I was a teenager when the service ended...
Thoughts from MACTRAXX
EXPRESS TRAIN TO NEW YORK PENN STATION-NO JAMAICA ON THIS TRAIN-PLEASE STAND CLEAR OF THE CLOSING TRAIN DOORS