Source: Railroad Gazette
This NBER data series m03004 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03004
Release: NBER Macrohistory Database
National Bureau of Economic Research, Eastbound Freight Shipments for Chicago, IL [M03004US16980M605NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M03004US16980M605NNBR/, September 5, 2015.