There are two railroad lines that intersect at Bryn Mawr & Kostner in Sauganash.
The Valley line stopped being used in the early 1990s and in 2003 there was a process to start converting it to a bike trail (http://www.sauganash.org/biketrail/bryn_mawr-kostner_bike-trail.htm).
The other one was dismantled around June 2009. Here is some info. on it:
The Chicago Dept.of Transportation entered into a “railbanking” agreement with Union Pacific Railroad to use the out-of-service rail corridor east of Rogers Ave. for a new bike/pedestrian trail until a railroad might need the corridor again for rail service. Called the Weber Spur, the rail corridor runs from Bryn Mawr northeast to Devon. It crosses Peterson just behind Precision Plating Co. and crosses Pulaski at-grade just north of the abandoned car wash. The Village of Lincolnwood
has signed-on to extend both the Sauganash Trail (Valley Line Trail) and the Weber Spur Trail north to Touhy. In addition, the Sauganash Trail will be extended south through the forest preserve from Bryn Mawr to Lawrence.