Daily Average Through 1934. Mid-Month Figures Were Computed Based On Given End-Of-Month Figures. New York Central Figures Were Not Available For 02/1920-12/1920; Missouri-Pacific Figures Were Not Available For February And March Of That Year; Fort Smith And Western Figures Were Not Available For March Of That Year. Switching And Terminal Companies Were Excluded Through 1936. The Figure For January 1937 Is The Average Of 12/1936 (Excluding The Companies) And 01/1937 (Including Them). The Companies Are Included Outright Beginning In February Of That Year. Source: Interstate Commerce Commission, Freight And Passenger Service Statistics Of Class I Steam Railways In The United States For 1920-1934 Data: 1935-1942 Data Are From Icc, Motive Power And Car Equipment Of Class I Steam Railways In The United States.
This NBER data series m01250 appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: m01250
Release: NBER Macrohistory Database
National Bureau of Economic Research, Total Locomotives Assigned To Freight Service, Class I Railroads for United States [M01250USM480NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M01250USM480NNBR/, August 2, 2015.