The civilian labor force is the sum of employed and unemployed persons.
The series comes from the 'Current Population Survey (Household Survey)'.
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Civilian Labor Force - 1-3 years of High School, 45 to 54 years, Men [HS13LM4554], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/HS13LM4554/, June 30, 2015.