If there was any doubt about the pent-up U.S. demand for doing business in Cuba, Cargill Inc.'s story might clear it up.

The Minnesota-based international agricultural conglomerate started eyeing Cuba with interest, and preparing for a policy change, more than a decade ago. Last year, it started meeting with like-minded organizations to advocate lifting the half-century-old U.S. embargo on trade with the island.

They were just about to announce the formation of the U.S. Agricultural Coalition for Cuba when they—and just about everybody else—got a surprise. On Dec. 17, President Barack Obama and President Raúl Castro announced a historic thaw, and the promise to try to restore normalized relations.