WYSIWYG, I dislike Wackipedia because it has errors in many of its posts, but see its article on Cargill, perhaps the biggest player, not only in corn, but all massive agricultural enterprises. According to Waskipedia "the world's second-largest privately held corporation..."; "responsible for 25% of all United States grain exports," "supplies 22% of the United States meat market," etc. It is a producer of ethanol and other products.
Descendants of the family still control 85% of the company. Annual income over 80 billion dollars.

Although presented without proper documentation, much of the article can be verified through other online sources, and is a good brief introduction to an American giant.

It is now a large player in financial operations and hedge funds. It is a major exporter from Latin American and Asian countries as well as from North America. It is a major lobbyist in Washington and other capitals, supporting free trade.

Its large holdings are difficult to sort out- a forest of interlocking entrprises and land and corporate holdings. Being privately held, there are no public stockholders and public disclosure of practices is held to a minimum. They have a website, which presents their public face.