Created by the 1975 merger of Sigma Chemical Company and Aldrich Chemical Company, Sigma-Aldrich since grew through various acquisitions until it had over 9,600 employees and was listed on the Fortune 1000 at the time of its acquisition by Merck. The company is headquartered in St. Louis and has operations in approximately 40 countries.
In September 2014, the German company Merck KGaA announced that it would be acquiring Sigma-Aldrich for 17.0 billion dollars. The acquisition was completed in November 2015 and Sigma-Aldrich became a subsidiary of Merck KGaA. The company is currently a part of Merck’s life science business and in combination with Merck’s earlier acquired Millipore, operates as MilliporeSigma