Series Is Presented Here As Two Variables-(1)--Original Data, 1921-1929 (2)--Original Data, 1929-1949. Source: Employment And Payrolls, January 1938, U.S.Department Of Labor, Bureau Of Labor Statistics, And Following Monthly Issues For 1929-41, And On 2) The Monthly Labor Review From The Bureau Of Labor Statistics For 1942.
This NBER data series m08249b appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08249b
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Employment, Anthracite Mining for United States [M0849BUSM340NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M0849BUSM340NNBR/, July 6, 2015.