On the morning of December 7, 1941, Japanese bombers staged a surprise attack on U.S. military forces at Pearl Harbor in Hawaii. Sixty years after the attack on Pearl Harbor, the United States was attacked again. On the morning of September 11, 2001, four commercial airplanes hijacked by 19 terrorists killed nearly 3,000 people when they crashed into the two towers of the World Trade Center in New York City; the Pentagon near Washington, D.C.; and a field in Shanksville, Pennsylvania. Four years after Pearl Harbor, Congress created the Joint Committee on the Investigation of the Pearl Harbor Attack. Five months after the 9/11 attacks, Congress created a joint inquiry to look into intelligence failures before and after the attack. Then in November 2002, Congress created the independent National Commission on Terrorist Attacks Upon the United States, popularly called the 9/11 Commission, to thoroughly investigate the attack. The recommendations adopted from both post-investigation reports had far-reaching impact and informed important changes in the structure of the federal government. The study of the two featured documents will illustrate for students the importance of Congress's power to investigate as part of a system of checks and balances established by the Founders. (Contains 14 notes.)