Closings and cancellations following the September 11 attacks

Many closings and cancellations followed the September 11, 2001 attacks, including major landmarks, buildings, restrictions on access to Lower Manhattan, as well as postponement or cancellation of major sporting and other events. Landmarks were closed primarily because of fears that they may be attacked. At some places, streets leading up to the institutions were also closed. When they reopened, there was heightened security. Many U.S. states declared a state of emergency.