U.S. Railroad Retirement Board Office of Public Affairs 844 North Rush Street Chicago, Illinois 60611-2092 http://www.rrb.gov/geneal.htmlhttp://www.rrb.gov/geneal.html
The board only has information for 1937 on and from what I can tell they prefer if you can provide a social security number when you request information.In my case, my ancestors didn't fall into post-1937 and they didn't have a social security number so I never wrote to them.
Chicago & North Western Historical Society http://www.cnwhs.org/http://www.cnwhs.org/ This is one of the historical society pages which provides some good background information on the railroad.
I wrote to the Chicago & North Western officeduring their purchase by Union Pacific.They really didn't have any information; they were very nice to deal with though.I don't know if Union Pacific would be as helpful but their home page is http://www.uprr.com/http://www.uprr.com/ and their address is: Union Pacific Railroad; 1416 Dodge Street; Omaha, NE 68179; UPRR Main Number: 402-271-5000.
In addition, I found the following websites that talk about the Brotherhood of Railroad (Railway) Trainmen which appears to be the same group you mentioned.