In 2007, The Heritage Foundation became the first and only organization tracking thwarted terrorist attacks against the United States. That year, Heritage reported that at least 19 publicly known terrorist attacks against the United States had been foiled since 9/11. Today, that number stands at 40. The fact that the United States has not suffered a large-scale attack since 9/11 truly speaks to the country’s counterterrorism successes. However, simply applauding the achievement and taking only a forward-looking approach is not nearly enough to prevent the next attack. Reviewing the terrorist plots that have been foiled since 9/11 can provide valuable information for understanding the nature of the threat, as well as best practices for preventing the next attack.