 Oil spill in Gulf of Mexico On April 20, an explosion sank the British oil giant BP’s leased Deepwater Horizon rig on the southern Louisiana coast in the Gulf of Mexico, killing 11 workers. During the ensuing five months, more than 4 million barrels of oil gushed into the Gulf of Mexico, making it the worst oil spill in U.S. history and causing tremendous harm to the Gulf ecosystem. | 