Monsanto, a company based in St. Louis for more than 100 years, is now part of Bayer.
The roughly $63-billion acquisition closed Thursday, nearly two years after the companies first announced the deal. Regulators in Canada and Mexico were among the last international watchdogs to approve the combination.
The U.S. Department of Justice signed off on it late last month after Bayer committed to shedding about $9 billion in several areas to chemical giant BASF.
That includes Bayer's Liberty-brand herbicides, which compete with Monsanto's Roundup.