American equestrian and heiress Gwendolyn Sontheim Meyer has an estimated net worth of $5.5 billion as of April 2016 according to Bloomberg. Most of her net worth is derived from their family business, Cargill Inc. Gwendolyn Sontheim Meyer currently lives with her husband in Rancho Santa Fe, California. The couple has two children together.

She is the daughter of Marion MacMillan Pictet (deceased) and the great great granddaughter of Cargill Inc.'s founder William W. Cargill. As of the fiscal year 2012, the Cargill Inc's revenue is estimated to be around $134 billion, making it the largest privately held company in the U.S. This agro-giant company operates on several areas including food production, cattle, crops, commodity trading and even risk management. Since the taking over of William W. Cargill's son in law, John MacMillan, in 1909, the CEO position was always assumed by a family member, but only until 1995. Today, the majority of the company is still owned by the family.