Illinois Northern was a Chicago area short line that ran from McCormick Station (east of 26th Street Crossing) to a connection with the north end of Grand Trunk Western's Elsdon Yard. Originally owned by International Harvester, by 1971 most of its stock was owned by the Atchison, Topeka & Santa Fe, which later took over operations. The line was finally abandoned in 2010.
Here at 26th Street Crossing is caboose no. 1641 and one of the six Alco S-4 switchers (no. 31) that made up the road's roster at the time of the photo.