The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNS11300060
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Civilian Labor Force Participation Rate: 25 to 54 years [LNS11300060], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNS11300060/, July 30, 2015.