Data For 1921-1932 Include Switching And Terminal Companies; Thereafter These Areas Are Not Covered. Source: Interstate Commerce Commission, Wage Statistics, Statement M-300.
This NBER data series m08177 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08177
Release: NBER Macrohistory Database
National Bureau of Economic Research, Man-Days Paid For, Railroad Employees For Whom Days Are Reported for United States [M08177USM552NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08177USM552NNBR/, July 29, 2015.