The Bureau of Labor Statistics (BLS) does not seasonally adjust this series. Although the Federal Reserve Bank of St. Louis seasonally adjusts series whenever possible, the current nature of this series does not allow for such an adjustment.
Source: US. Bureau of Labor Statistics
US. Bureau of Labor Statistics, All Employees: Information in Sioux Falls, SD (MSA) [SIOU646INFON], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/SIOU646INFON, February 5, 2016.