Source: Bureau Of Labor Statistics, For 1919-1930 Data: Bulletin No. 610, Pp. 104, 69-70; For 1931-1934: Mimeographed Release, September 1938, "Revised Index Numbers Of Factory Employment And Payrolls"; For 1935-1939: Mimeographed Release, May 1940; For 1940-1942:"Employment And Payrolls" And Monthly Labor Review.
This NBER data series m08103 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08103
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Factory Employment, Boots and Shoes for United States [M08103USM331NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08103USM331NNBR/, July 28, 2015.