Series Is Presented Here As Two Variables--(1)--Original Data, 1921-1937 (2)--Original Data, 1937-1943 Data Exclude Switching And Terminal Companies. Data For 1921-1935 Are Based On Daily Averages; 1936-1937 Are Mid-Month Figures Computed From End-Of-Month Data. Source: Interstate Commerce Commission, Data For 1921-1933: Direct From The I.C.C. Data For 1934: Freight And Passenger Car Operating Statistics. Data For 1935-1937: Motive Power And Car Equipment Of Class I Steam Railways In The U.S.
This NBER data series m01258a appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: m01258a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Serviceable Passenger Locomotives for United States [M0158AUSM365NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M0158AUSM365NNBR/, August 27, 2015.