Release: NBER Macrohistory Database
Switching And Terminal Companies Are Excluded Through 1936. They Were Included Beginning In 1937. The Figure For January 1937 Was Derived By Adding The 12/1936 Figure (Excluding The Companies) And The 01/1937 Figure (Including Them) And Dividing By Two. Source: Computed By NBER By Adding Series (Locomotives Assigned To Freight And Passenger Service, Respectively).
This NBER data series m01273 appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: m01273
National Bureau of Economic Research, Total Number of Locomotives Assigned To Freight and Passenger Service for United States [M01273USM481NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/M01273USM481NNBR, March 25, 2017.