Data Are Referred To By The Source As "Man-Hours In Nonfarm Establishments, All Employees." Source: Bureau Of Labor Statistics, Business Cycle Developments, February, 1968 Issue For 1947-1964 Data; August, 1968 Issue For 1965 Data.
This NBER data series m08340 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08340
Release: NBER Macrohistory Database
National Bureau of Economic Research, Manhours of Nonfarm Employees for United States [M08340USM248SNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08340USM248SNBR/, July 30, 2015.