Data Are Based On Average Carloadings Per Working Day. Source: Data For 1920-1953: Federal Reserve Board, Bulletins For June 1941 And Thereafter
This NBER data series m03031 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03031
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Freight Car loadings, Miscellaneous for United States [M03031USM343NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M03031USM343NNBR/, November 30, 2015.