On April 20, 2010, the Macondo well blew out, costing the lives of 11 men, and beginning a catastrophe that sank the Deepwater Horizon drilling rig and spilled nearly 5 million barrels of crude oil into the Gulf of Mexico. The spill disrupted an entire region’s economy, damaged fisheries and critical habitats, and brought vividly to light the risks of deepwater drilling for oil and gas—the latest frontier in the national energy supply. Soon after, President Barack Obama appointed a seven-member Commission to investigate the disaster, analyze its causes and effects, and recommend the actions necessary to minimize such risks in the future. The Commission’s report offers the American public and policymakers alike the fullest account available of what happened in the Gulf and why, and proposes actions—changes in company behavior, reform of government oversight, and investments in research and technology—required as industry moves forward to meet the nation’s energy needs.