Series Is Presented Here As Three Variables--(1)--Seasonally Adjusted, 1929-1942 (2)--Seasonally Adjusted, 1940-1946 (3)--Original Data, 1947-1966. Beginning In April 1962 Labor Force Estimates Are Based On The 1960 Population Census. Source: Employment And Earnings And Monthly Report On The Labor Force, Vol. 13, No. 9, March 1967.
This NBER data series m08292c appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08292c
Release: NBER Macrohistory Database
National Bureau of Economic Research, Unemployment Rate for United States [M0892CUSM156NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M0892CUSM156NNBR, February 12, 2016.